If a style developer wants to remove the comments area of attachments they immediately break that functionality. This is because assets/javascript/plupload.js is looking for that specific HTML control to add the needed hidden inputs right after it:
https://github.com/phpbb/phpbb/blob/3.2.x/phpBB/assets/javascript/plupload.js#L214

Should probably look for some other element in the row or not look for anything at all and just add to the end of the row.