What? do have to donate 10 btc to change username? This is an unreasonable amount
Yes, it is a direct line but no longer used for a long time. The last donator is Claymore in 2017 and Claymore did that donation not to change username.
Else, if you have reasons to change your username for privacy, you will get apporved and it is free.
If it is because privacy, you will have both changes, username and display name.
If it is for display reason only, you will have only display name change and your username will be the same.
Maybe they didn't donate 50 BTC but were gifted the VIP status because of their contribution to Bitcoin and the forum.
Right. I posted about this somewhere when I did it.
IIRC MagicalTux also got VIP without paying 50 BTC because he contributed significant resources in other ways.
Each user has a display name, which is the only name ordinary users see, and a username, which is what you use to log-in with. Almost always, they are the same.
If I change a name for reasons of appearance, then I only change the display name. The username remains reserved, the user can still login using the username, PMs can still be sent to that username, "search member" allows searching for the old username, etc.
If I change a name for reasons of privacy, then I change both the username and the display name. In this case, it is possibly hazardous to reserve the old username, since it allows someone to test for the existence of that username, possibly defeating the privacy benefit. If you're worried about being impersonated, then simply don't seek to have your username changed.