At the moment, it's a mess of manually generated HTML. We should tidy it up and use FormSpecialPage, because it is indeed a special page with a form.
|Open||None||T49145 Formally deprecate jQuery UI after we've stopped using jQuery UI in extensions and core (replacing it with OOUI).|
|Open||None||T100270 Replace use of jQuery UI and MW UI with OOUI across all Wikimedia-deployed extensions and core|
|Open||None||T122014 Convert all extensions/skins to OOUI|
|Open||None||T28751 Extensions that should really be core functionality (tracking)|
|Open||None||T27482 Merge RenameUser into core|
|Open||Sethakill||T100263 Refactor Special:RenameUser to use FormSpecialPage|
I've rewrote this page to use FormSpecialPage with OOUI. I've added warning if user is blocked for indefinite time (can be changed) instead of 'Show block log for user' button. IMO it looks better.