we’ve been blocked by precisely one actual instance - the predominantly German-speaking feddit.de

Which also was my first home instance until I noticed that a comment chain I accidentaly started using another lemmy instance was not visible when looking at the thread though feddit. Not even my own comments made with an instance that wasn't blocked. Turns out the user I answered to start that chain was a member of your instance and thus the comment and everything following it was not visible for feddit users.

Which is why I'm a full time lemm.ee user for now bc at the time it had 0 blocked instances and was blocked by 0 too^^

and most importantly, the admins here have explicitly stated that the policy is to avoid defederation at all possible avenues.

That's the policy of lemm.ee too. It has 34 blocked instances right now but those are all suspicious ones that formed and got >30K users within a couple hours and no activity at all.

But ultimately, new users shouldn't have to worry about such things, which is why I can't see Lemmy growing as a whole with the tools available now.
Everywhere it says it's not relevant where you sign up because you can see all the stuff from other instances anyway, but that's simply not true, it DOES matter where you sign up and even after that you could be forced to change your instance when the defederation roulette starts spinning again.

and most importantly, the admins here have explicitly stated that the policy is to avoid defederation at all possible avenues.