Is there any way to view a formatted comment prior to posting it? It is possible to copy, delete, paste, and try to fix the formatting if it goes wrong, but "fixing the formatting is not trivial.
Here's what I do.
You can check your comments before posting them by using the preview window.
Simply click on a question and go into answer mode, i.e. click anywhere in the answer field. As you know, this will bring up the editor.
You can now copy your comment and paste it into the editor. You can use the preview window to check the math formatting.
After you're done, simply copy the comment and paste it back in the comments section of the question you want to comment on.
To close the editor, click on the Cancel button.
You can even write the comment in the editor, copy it and paste in the comments section of the question you want to comment on.
Now, I'm not really sure I follow the part about
and try to fix the formatting if it goes wrong, but "fixing the formatting is not trivial
so let me know if this is not what you're looking for, I can edit this answer accordingly.