Follow-up from "Allows any user to comment on a dismissed vulnerability (Dismissal reason: Step 3)"

The following discussion from !12067 (merged) should be addressed:

• @pslaughter started a discussion: (+8 comments)

  suggestion: Now I see that the contents of this template are very similar to what's going on inside <dismissal-comment-box>. IBH, it's a little weird what's going on here...

  From what I can tell... When isCommentingOnDismissal is false, we render a text area with a grey background. When that grey text area is focused we dispatch an action that updates isCommentingOnDismissal to true, which unmounts the grey text area and mounts a new one 🤔...

  Why not just have one text area and update it's class / value conditionally? I'm pretty sure this would take less code (especially test code) 🤔.