I race changed my Pandaren Shaman to a DID, i also changed the name from Hanhoi to Hán however on the forums it shows that the character as a DID yet the name is still Hanhoi.
Nothing I’ve tried has fixed it so far.
The forums don’t communicate that closely with the main WoW systems, so they don’t “know” about your character’s identity change. At some point, the new name will show up in the list of characters you can post as. It will just take time. No one has found a reliable way to cajole the website services to immediately update to in-game reality.
A related fact: the forums have no way of knowing that Hán used to be Hanhoi. Hán will effectively be a new forum poster, and will have no connection to post history or trust level Hanhoi may have established.