Wouldn't it be nice that for those users who have their preferences including (custom) sig at Meta to get this global as well so with e.g. a UserNameChange one does not have to change the SigWikiText in those prefs at all wikis, but only in Meta?
Topic on Talk:New requirements for user signatures/Help
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It looks like that feature was requested in 2018, at phab:T188200.
Ok thx, I'll have a look there soon