Hiya!
Ok, didn't read through everything, but I did read a lot and I think I have the gist of what a lot of folks are saying. For the most part, I agree.
!!!WALL OF TEXT BELOW!!! >Proceed to very bottom for Summation<
I really quite like "bounded accuracy" being nice and low with a smaller number range.
Back in the day, there
weren't any such thing as "skills" or "proficiencies". We eventually got "Secondary Skills" once the AD&D DMG came out (can't remember the year, but dang was that book amazing when it did come out...still is, actually...). Secondary Skills were optional, specifically listed as such (which was rare; just about everything in AD&D was default 'optional'). They were broad-reaching categories of what you did prior to deciding to wander into deep caves, kill monsters and take their treasure. Things like "Armorer", "Scribe", "Tanner", "Sailor", etc. Any time something came up in game where the
player figured his characters background might help, he was to bring it up and come up with a reason why he should be allowed to do it or get a bonus to do it. So if you were a "Sailor" and everyone in the party needed to cross an obviously very old rope bridge across a bottomless crevasse in a wet cave somewhere deep down in the lands of Deepearth, you could pipe up and say
"Danswig used to be a Sailor back before he was a Fighter, where he dealt with ropes and knots all the time. Can he tell if the ropes are still good, and if the knots are tied well?"... and the DM then did his DM job and made a reasonable, educated guess. DM:
"After examining the rope and knots, Danswig figures the ropes are on their last legs. Knots are solid and doubled up, but the strength of the rope probably won't hold weight in excess of a large man". And that was that.
Nowadays, we have specific "Skills" to handle the specifics. It has gone from very broad, to very narrow. As such, a more consistent numbering system had to be developed. It was still pretty 'broad' in the Wilderness and Dungeoneers Survival Guide books for 1e; 2e narrowed a bit more with more skills/proficiencies; 3e took that to the extreme almost, with a slightly lowering of the number of skills, but
vastly increasing the numbers; 4e...don't know, I avoided it like the plague. Now we have 5e, that has reduced the skills a bit, and also reduced the numbers.
What has remained consistent? Players asking
"Hey, my character knows [this]...can he determine [that]?". What 5e has done, is kind of mix the best of both worlds. The more 'broad' definition of skills (re: "Athletics", "Arcana", "Slight of Hand", etc), with a specific numerical value that increases and can be increased. What BA has done with this is allow a wide range of play styles to adapt the rules to what they need to run the game they want. A DM could say that only those with actual Proficiency in a skill can make a roll, or that other can as well, but at disadvantage. Or a DM could say everyone can make any roll and add their level proficiency bonus, but those that have the skill can roll at advantage. Or a DM could decide to not even use skills at all.
Because of BA, those changes are not likely to vastly change other things in the game, and if they do, because of the lower numbers and lower range/effectiveness/whatever, it becomes trivial for the DM to adjust "on the fly" during a game (e.g., a DM not using skills at all comes across
"PC's may make a DC 14 Arcana check to know they type of rune-magic mentioned", the DM can just decide that only the Warlock in the group can know about that, or maybe the elf, or maybe even the dwarf if the rune-magic is ancient dwarven magic used before the dawn of time, when dwarves still knew how to use rune-magic, or whatever fits his style of campaign).
If we look back at 3.x/PF, a DM can't really "remove" skills from his game without some serious consequences. The integration is too vast, and the numbers too big and 'important'. Skill bonuses in PF can range from the "low end" of +3 to +5, up to the ridiculous (like, +27, +33, or +40). Removing skills suddenly shifts the implied capabilities of creatures/PCs/NPCs down to "none". Seeing a creature with +35 Climbing would now become a creature that can climb. But so can the lame dwarven cleric, she can climb too. Her Climb score of -1 would become just as 'deterministic' as the creatures Climb of +35. Basically, throwing a huge monkey wrench into the system expectations, not to mention classes that rely on skills and skill points as a feature (I'm thinking of the Rogue).
Anyway... Now that I've said my peace about BA in regards to Skills, we can pretty much apply the same thing to combat and saves. Because of the smaller number range, it makes it easy for a DM to adjudicate things during game and maintain a solid consistency throughout the campaign. If the DM decides that fighting on a slanted rooftop gives -2 to hit unless the character is using a Finesse weapon, it's easy to equate that to giving a -2 to hit while fighting on the rolling deck of a galleon at sea, or giving -2 to hit while sliding down a steep hillside and trying to maintain your footing (with an additional Acrobatics check to remain on your feet). Doesn't matter if the characters are level 1, level 10, or level 20. It's always -2 and that -2 is always going to make some kind of difference. The DM doesn't have to "up" the numbers to make it challenging, and it also saves the total disconnect a DM may get (like myself) when I feel I have to up that -2 to -10 just because the characters are level 15. Why? Why is fighting on the rooftop
this time -10, when a year ago fighting on the same rooftop it was only -2? Without BA, this is what you would have to do or just be content with nigh-pointless rolling of the d20 (e.g.,
"Acrobatics? At -2? Err....ok... I rolled a 9, so... made DC 28").
My House Rule on Skills: Here's what I do. Pretty much by the book, but if you don't have actual Proficiency in the skill, if you succeed, you
barely succeed with minimal results or short-lasting ones. So two characters make an Arcana check to figure out that those markings are dwarven rune-magic. The guy
without the actual Proficiency knows they are dwarven and were some old kind of dwarven rune-magic, probably some kind of protective magic. The guy
with the actual Proficiency knows that these dwarven rune-magic markings were made at the end of the dwarven Age of Magic, about 3,000 years ago and that these ones were created by a clan of dwarves who are not normally found in this area; furthermore, these runes still hold latent, but active, magic, and someone with dwarven blood and the proper magical training may be able to activate them again to re-shield the area from divination spells.
By using skills this way, it still will
always pay to have Proficiency in something, even if someone else has a higher non-proficient score. In my above example, the rating of the characters Proficiency is irrelevant; the non-proficient character could have had a +6 and the proficient character could have had a +4; the proficient character would
still "know more".
When we first started playing, I used the "Adv/Disadv" mechanic; Adv if you have it, Disadv if you didn't. But that feelt too much like "double dipping" (and it basically was), so I switched to a more non-mechanical way of handling it. Something that encouraged role-playing and not roll-playing. My current way (as mentioned above) seems to have handled this quite nicely.
Now, my only beef with BA is that it didn't carry over into Hit Points.

At level 6, one of my players PC had something like 90hp or something! Monsters, the "tough" ones, had HP's numbering between 120 to 250hp...at
6th level! This feels...wrong, to us. I understand the reasoning...BA reduces AC importance a bit, so in order to make some creatures 'tougher', they had to do something...increasing HP's was the easiest and most consistent way to do that. However, I really wish they would have put in some other method of HP calculation or damage mitigation in the Monster Manual or the DMG. I'm toying with various ideas (like Critical hits doing "%-of-max-HP" in stead of flat HP damage...so doing 24 damage equates to 24% of creatures max HP; unless that number would drop it to 0 or lower; if ever dropped to 0 or lower via a Critical, yer dead. Mark off all three Death Circles. Instantly). Anyway, we haven't hit levels above 5th/6th, and this is just now starting to come to light.
Wowzers! That's a LOT of text! Sorry guys...
Summation: I like BA. Skills work fine with BA. Combat too. Give other benefits for having Proficiency to make having it always better than not. HP's are the biggest bugaboo with 5e, IMHO.
^_^
Paul L. Ming