One huge problem with Discord's block feature is that a blocked user can easily discover they have been blocked by simply trying to react to your post and letting users know they have been blocked is a TERRIBLE idea.
See, there's a lot of insufferable people online who tend to get blocked and then endlessly whine about it or take it as some sort of personal challenge, which then makes other people talk about it, people might ping or DM you directly about it, some people even insult you for being so intolerant and sensitive that you have to block a user who's "just expressing themselves" or even try to SHAME you for blocking them and so terribly upsetting the poor snowflake and hurting their precious wittle feewings...
Anyway here's my suggestion:
Let blocked users add reactions to your posts, but make their reactions invisible to everybody else. You can't see them, other users can't see them, even admins can't see them - but the person you blocked CAN see them.
If a blocked user adds a common reaction like :heart: or :thonk: and then a second person that ISN'T blocked adds that same emote, simply show the blocked user two of that react but everyone else only sees one.
(Discord should really do something similar if a blocked person DMs you too, but hey, one step at a time.)