Thread:Support/About MediaWiki:Mw-ui-feature-user-count/en

In the first parameter there's "one user is", which means that if there are 21 users, it will show not "21 users are", but "One user is". So I suggest changing this line to "$1 user is" and adding another, if this works, of course. In some languages the translation for 1, 21, 31, 41 ... users would be the same. But now instead of all these numbers it shows only "One user is", which is wrong. So this message should be improved somehow not to confuse the translators that aren't aquainted enough with magic words.