I changed the CSS and Javascript in the "Advanced Editor" to clean it up. This is also the editor seen in "New Thread" and "New Reply". Basically I got rid of the mouseover style changes which were messed up due to vB legacy JS code from a decade ago.
While doing this change, I then completed the first phase toward changing the attachment form to a Bootstrap Modal, but did not complete the change because I need to get rid of all the table elements first (there are quite a few). However, I did manage to add some Bootstrap classes and cleaned this form up as well:
I don't want to spend too much time on this, because I plan to change this entire method of uploading attachments to the forums, but this does clean it up a bit.