You experience on combining rules from different editions

[Stormonu]

I prefer to avoid rules mish-mashing of any sort; I have enough trouble remembering one system that I dislike mixing rulesets and getting them confused.

Those times In my youth when I did try to mix systems, it turned out poorly (I remember one attempt of crossing Gamma World and D&D rules - it didn't pan out at alll - the group got slaughtered by a combot, despite the fact the Pc knights were carrying laser swords). So I guess I stopped trying.

 

[kitsune9]

I combined the mutation rules from Tome of Corruption (WHRP 2e) with my Pathfinder game. It worked pretty good as I just had to make a few conversions on penalties and saving throws, but overall the tables worked just fine.

 

[Wycen]

It makes for sometimes non-conversations or half-truisms. You see, I play in such a game now, but I'm the only one who knows this.

The people I play with on Wednesdays are old friends who've all played previous editions of DnD. They call it Pathfinder, but they add weird rules like "attacking from behind for +2", not realizing that spell like abilities provoke attacks of opportunity, all animal companions/familiars being anthropomorphosized, etc.
The half-truisms come from a player saying "you can't touch me" after casting Protection from Evil when facing ghouls who are of course evil, but not summoned creatures. The DM likes to repeat the story of her evil drow monk being next to another PC who casted Protectiion from Evil and she likes to point out "I took a five ft step away from him" blah blah blah.

I generally have fun so I don't point out how they have veered from the straight and narrow, but sometimes I have to swallow my tongue and shut up. It's part of why my analysis on the Carrion Crown AP in the Pathfinder forum here is slow and sometimes awkward.

 

[Desdichado]

It makes for sometimes non-conversations or half-truisms. You see, I play in such a game now, but I'm the only one who knows this.

The people I play with on Wednesdays are old friends who've all played previous editions of DnD. They call it Pathfinder, but they add weird rules like "attacking from behind for +2", not realizing that spell like abilities provoke attacks of opportunity, all animal companions/familiars being anthropomorphosized, etc.
The half-truisms come from a player saying "you can't touch me" after casting Protection from Evil when facing ghouls who are of course evil, but not summoned creatures. The DM likes to repeat the story of her evil drow monk being next to another PC who casted Protectiion from Evil and she likes to point out "I took a five ft step away from him" blah blah blah.

I generally have fun so I don't point out how they have veered from the straight and narrow, but sometimes I have to swallow my tongue and shut up. It's part of why my analysis on the Carrion Crown AP in the Pathfinder forum here is slow and sometimes awkward.

See, I have absolutely no problem with those kinds of houserules. I mean, I don't literally agree with some of them, and wouldn't prefer them, but I have no problem with them conceptually.

I do have a problem, however, if it's as you imply and your group doesn't even know that those aren't the rules. If you're not even all playing the same game because the rules are supposed to be Pathfinder but come kind of half-remembered ruling from years ago gets applied to situations all over the place that I can't expect or anticipate, then that's got to be pretty frustrating.