Doubling it here from dev dairy:
Please add tags or categories to civics that would restrict them.
Tags should denote behaviour of specific civic. This might be something like MUST_PURGE or DIPLOMACY_FORBIDDEN. Other civics should be able to check it (ie civic_tags = { NOT = { value = MUST_PURGE } } for syncretic species. It could also be effective to shift certain mechanics to civics files, where they are easily managed. For example, if I create new kind of civic that would forbid diplomacy like in Inward perfection, I'd have to go somewhere where rules for diplomacy are kept and overwrite it. What if instead those rules simply said "NOT = { has_civic_tag = DIPLOMACY_FORBIDDEN } - then everyone can add as many such civics as they feel like.
Category should be visible on civics and tell you you can only pick one. For example, servitors, terminators and assimilators should all have SPECIAL_MACHINE category. Should I add 10 more unique machine behaviours in my mod, they'd all have the same category instead of ever growing NOR that can't be properly coordinated between mods.