@Starcross@mk.absturztau.be It depends on the ActivityPub servers and clients involved, of course, but it probably does not. Based on my interpretation of 6.9 Block Activity, servers should not pass on the Block activity, so the target actor would not know to Delete, and there is no recommendation to Delete upon receipt of a Block.
fediverse question: if you block someone, does that delete their reply from your original post?