You still haven't proven that a rule not listed as optional was specifically an optional rule. All the two different non-optional rules from the PHB and DMG prove is that between the year the PHB was release and the DMG came out, Gygax had second thoughts about dying at 0 and changed the rule.
Just because your own personal interpretation made 40 years after the fact wasn't how it was ruled, played, or even STATED in the DMG doesn't make your ideas true...nor do the others who never seemed to actually seen how it was officially ruled.
In addition, as I said, the official rule for it is actually in the PHB (the one the players actually were supposed to have read, the DMG was for DM's eyes only. As far as players read, the official rules are in the PHB, with things that go contrary to it as a DM's option for DM's eyes only).
If you don't like the OFFICIAL rules of the PHB (page 105) that's your own call. However, trying to say 2e was more deadly than 1e is more of your own personal interpretation rather than anything based on how it was played or done.
It's actually ironic as my stance wasn't that 1e or 2e is actually more deadly...but it is as per the DM.
Which means, if you really are disagreeing with my assessment, you are VERY modern and saying a campaign is more deadly because players want it to be deadly than how the DM rules or decides.
I was POINTING OUT that the statements about the rules were actually incorrect. People are trying to read 1e like they did 4e...but 1e was nothing LIKE 4e was in how rules were read or interpreted.
The original rules were normally interpreted more openly overall, but played with OD&D or Holmes (DMG didn't come out for a while). The DMG was made plain that it was options.
As per the 1e DMG the DMG was for the DM's eyes only (players who read it were worthy of death!!). Players expected it to be played as per the rules they knew (and the Zero HP rule is NOT in the PHB). However, why then include the ideas of the DMG? The ZHP is prime example.
As per the DMG again (and you SHOULD know this, if you had ever actually took the time to READ the DMG), players who expend all their options may be discouraged or not want to play. For example, if they have planned and spent time to get to a dungeon, only to have wandering monster after wandering monster rolled up and take up all their resources making their planning moot, that can be very discouraging. Thus the DM has to be able to be the arbitrator of the rules and know what and how much.
Thus, being able to relax (or to make stricter) the rules are the DM's realm. Everything in the DMG is basically a toolbox for the DM to use. There are many contrary rules that may not seem to work with each other (for example, the official death at 0 HP of the PHB, and the ZHP rule) or contrary to each other at first glance, but can be integrated given someone actually understands them. However, the DMG overall is simply a toolbox for DM's, one of the greatest ones that has ever been made.
Even 2e players knew this...not sure why several on these forums seem to have no idea (or purposefully ignoring this and trying to read it as a 4e DMG rather than how the 1e DMG was utilized as) of this. This is NOT some new idea or something mysterious or unknown, this is pretty common knowledge.
That's why the ZHP was an optional rule, with the PHB rule being the default or core rule.
Of course, the DM could use whatever options and ideas they wanted, but the default was nothing like the Death's Door optional rule of 2e.
Not that it really matters, except those who for some reason want to prove 2e was more deadly (which it really wasn't, a great argument could be made that the way it was played eventually in 1e with thieves skills, especially remove traps, was FAR more deadly than a thief who chose to specialize in removing traps in 2e, or that a 1e Fighter got multiple attacks with specialization at 1st level vs. the core fighter in 1e, or that clerics got more special abilities, versatility, and possible weapons in 2e vs. those of 1e...etc).
Both (and even 3e) could be fairly deadly, and it really depended on the DM and how they ran the game. The rules listed really didn't have as big as an impact as the OP made them out to have had (and beyond that, most played death at 0 HP in both 1e AND 2e, and even if the ZHP rule was used, that was -1 HP...which isn't really THAT much of a buffer overall to make as big a difference as say...a Rogue triggering a trap because their Remove Traps skill was only 15% in 1e and the DM played it like that vs. the same DM with a Thief who had a Remove Traps skill of 40% in 2e who had a 25% better survivability rate with that DM in that accord).