This is "won't fix" thing as decision was made sometime ago to require JS in Misago.
oh! is there any way alert uses that they need to have JS enabled? may be a big text below top bar (and which is hidden by JS?)
<noscript>
with message on top of viewport would do it, but then decision would have to be made how to actually treat features that need JS. Display them broken? Or hide them?
or may be show it at the login itself and without that, no login option... well I do not know