What determines if a moderation action shows up in the modlog or not?
Sometimes I'll see a post deleted by a mod but there won't be a corresponding modlog entry for it.
Is logging at the discretion of the mod at the time of the action or are certain types of moderation intentionally hidden for safety? Some quirk of federation?
When banning an account, mods can also choose to purge all of its posts and comments. The individual deleted posts/comments don't show up in the modlog when removed in this manner.
That makes sense. I could've sworn I was looking for a modlog entry for a deleted comment by someone who isn't banned earlier but it's possible I got my wires crossed.
Is this the only scenario where it happens?
It's the only one that I'm aware of, though I can't say for sure that there aren't more.