How do you get in touch with someone who has you BL because of an honest misunderstanding? It's a small thing, but it woulkd be nice to have the chance to apologize and clear things up.

I'd say a third party would probably be best. If it WAS an honest mistake sombody shouldn't mind helping you out here

Just have a third party create a game between the two of you or start a message thread.

Honestly though don't worry too much about getting blacklisted except by really active top-tier players since they're not nearly as fungible as the average player. You don't even notice most blacklists.

Use an alt.

Send them a PM. They won’t get notified that you messaged them, but when they next check on their mail, your message would be marked as unread.

I thought you can't mail someone who has blocked you.