A user reported a bug where selecting a long subcategory in the mobile editor causes part of the editor to be hidden. The issue was initially unreplicable on test instances but was confirmed by another user when both category and subcategory names were long. The bug was fixed in a subsequent commit commit.
My forum has primary categories related to services, and subcategories further dividing each category, as this was carried over from a vBulletin instance.
When making a new topic on my forum using a subcategory, part of the editor is hidden from view.