Edit of user "Groove & Gothic MetalHead" on this page https://ru.wikipedia.org/wiki/TeXet?action=history can't be rolled back with this error message:
Cannot rollback last edit of TeXet by Groove (talk | contribs); someone else has edited or rolled back the page already. The last edit to the page was by Groove & Gothic MetalHead (talk | contribs).
Seems like rollbacking tool cuts rollbacked user username after first space, so engine assumes that these are different users.
I see the edit was reverted (using "undo" rather than "rollback", I think?).
I couldn't reproduce the problem on a local test wiki with a user named "Foo & bar". I clicked "rollback" and the edit was rolled back successfully.
I don't really want to, in case the rollback goes through and the user will be confused why someone with WMF in the username is reverting him. Does anyone other than you see the issue? It could be caused by a user script, gadget, or browser extension. Do you still see the issue if you view the page with JavaScript disabled in your browser?
Yes, it's caused by userscript that minifies wikilinks, excuse for troubling.
P.S. A common ruwiki user will not receive any information from (WMF) suffix. Only very experienced users know what it means.