It'd be neat if you could create conditional blocklists. Like only whoever X person AND Y person block will be blocked from my feed. And so on...

I don't think that'd solve the problem, but it would marginally help (and should be better than the status quo)

if they had a rule in the autoblock subscription that if a name appears in 3 or more (configurable) subscribed moderation lists it gets autoblocked, then users could stop following bad actors and change what moderation lists they use over time with less large impact to their experience. if you see messages from someone and they're on one of your block lists, you might reconsider the list. if they're on 2 you might consider personally blocking them, and if on 3+ you'd never see them. make blocks require a reason as well that the user will see alongside their block.

Then unsubscribe from that blocklist.

Does that unblock whoever got blocked by the rogue blocklist?

Yes, your combined blocklist is point-in-time. If you unsubscribe from a blocklist, a user on that blocklist will be immediately unblocked, provided they're not also on another blocklist you subscribe to (and that you didn't block them directly).

(Outside of eventual consistency, of course.)

Being 'at the whims' of whoever maintains the blocklist isn't unique to this style of moderation - when it's Twitter, you're at the whims of the company - but at least it means you can use other blocklists if/when the good ones go to shit, or can start a community-ran blocklist.

On Bluesky you have different algorithms/feeds which solves this problem. You subscribe to multiple feeds, which show you different content using different moderation and block lists. Sort of like you read different news sites and watch different news channels. Whatever feed you find that you enjoy the most is the one you spend the most time on.