In replying, editor shows "@mention" link in bottom right.
But it shows very few persons, "show 5 more" doesn't help since it can be used only once, total 10 persons.
Filtering is not working as expected. Typing "chris" after "@" don't show whom I'm trying to mention "Christian Schmitz" in the list.
I'm using browser context menu "copy link" and paste it for workaround, on Firefox.
Sometime typing "c" open "Create" menu in the top banner, I lost the position of editor.