Board Thread:Support Requests - Designing Your Wiki/@comment-26395974-20170222012545/@comment-25024589-20170222014457

The wikitext Algorithmz posted won't work on its own – there also is custom sitewide JavaScript involved. Annabeth and Percy made a detailed guide on how to get username insertion to work a while back, which you can view here.

However, as you, the OP, didn't specify the wiki, I don't know which one this is for. As such, I'll also give you a link to Special:Contact/general in case custom JavaScript isn't enabled on your wiki.