I get the same every ehre and there, especially if I use Chromium browser based mobile browsers like MS Edge or Google Chrome.
Often the "rectangle" at the addon comments or forum posts just are too wide to make a line break, espeically if there are big images which resize the whole post somehow.
Sometimes you can fix this by turning the screen at the smartphone. Often it does not help and there is no way to fix it as the buttons to edit/send a message etc are all moved out of the interactable screen bounds then due to this big images or long texts
Would be nice if the submit and reply and edit buttons etc. could be always stay at the left or something like that on Mobile browsers, and not centered (moved out of screen rects that way).