Apparently when Mac users try to play Diplo Infinity 2.8a, it crashes. This is well known to the diplo SC community; and selfish PC users don't care about this issue...

What are some ideas as to why a certain SC maps won't be compatible with mac? What triggers/terrain/units causes this?

Some EUD triggers will do it, though more often they'll just desynch, or if they're not shared, simply not do anything for the Mac users. It'll also happen as a result of techniques that rely on overflows, though these are rarely used in non-experimental maps.

More often, incompatibility is a result of either an incompatible protection method or corruption from certain editors (StarForge has been known to do this). The latter can be fixed by making no-net-change (i.e. doing and undoing) edits with a better editor, like SCMDraft2, until by chance you happen to "hit" the corruption; I've had some success fixing incompatible maps with this method.

Except that SCMDraft 2 won't work on OSX either, will it? Just play it on windows or linux. Trying to cater to the 1% is stupid, especially when most mapmakers don't have access to OSX.

Everything wich kinda "breaks" SC rules, such as EUDs and anything related to UnitID:## stuff, will cause Mac users crash. I'm almost sure it is because Mac's memory adresses are different than Window's adresses.

Not everything, but a lot of stuff having to do with buffer overflows will crash mac users. Heck, a lot of it crashes PC users, too.