I have tested against our largest instances and username autocomplete is super fast, especially on 1-letter username. What I am missing here?
Since we can’t use SiteSettings in the mention dialect, I pushed this fix to allow for any username length. It was limited to at least 2 characters before that. (cc @rumpelsepp)
https://github.com/discourse/discourse/commit/f654528aa464af268af6051e7699ba1eeee65cfb