m0useanswered grow question 10 months ago Blocking was not a useful feature on the site unless it was a chat. it only blocked your view of the individual messages and DM's, it did not prevent them from seeing your profiles or replying to anything you did. It was a half ass'd feature that should be reworked from the ground up.
FYI: it looks like you can block some DM's if they message you first, but you can not block if you initiated the message in the DM's. Also if you block someone and they have an active DM in your inbox, that DM will remain in your inbox but out of sight until you unblock them. I think this is so if you report it and block, GD has a log to reference. unknown if it removes it on the other persons side as well. more testing is needed.