What sort of thing most commonly provokes the anger of the typical Wikipedia admin?

Basically, anything that challenges "teh authoitah" of the admin to do as they did. This is a large part of the reason that "wikilawyering" and "disruption" are often used as pretexts for "indefblocks" and bans of the challenger. It rarely matters whether or not the admin is acting in direct contravention of a Wikipedia "policy" or "guideline". That is because "policies" and "guidelines" exist to provide the veneer, but not the reality, of a rational governance system. They are actually used as cudgels against "clueless noobs", heretics and the otherwise "unwiki", rather than as tools of rational governance.

As far as whether or not content is involved, that often depends on whether the challenge to the admin's action is content-based. If the article in question happens to be a pet article of the admin and used by them, or a pet editor of the admin, as a platform to promote "correct thinking" on the subject, then content can be said to be definitely involved.

Usually little things, like American vs. British spelling, or the correct Greek letter variant for a variable in an equation. Or linking or unlinking of dates. At least those are the things that have to do with actual content. But they're also angered when you vote against their proteges in Requests for Adminship.

Editing the pet articles that they list on their user pages.

In any way whatsoever. Add one comma or twenty paragraphs, they'll angrily revert you within seconds.

People like you who class us all as a corrupt power-hungry cabal.

So, either way it obviously says something bad about Wikipedia?

If it has much to do with actual content then they're content overlords with PHENOMENAL COSMIC POWER.

If it has little to do with actual content then they're just petty little ingrates stuck in an ITTY BITTY LIVING SPACE who get annoyed if they're not respected.

I mean, OBVIOUSLY they COULDN'T POSSIBLY be ordinary humans like the rest of us, right? They're genies and you just have to rub the lamp to get them out and fogging up the place, huh?

Be a sockmaster.