I'm tired of writing tags in the comments with my hands, and I did userscript, which adds formatting buttons to the comment field. It is not clear why they have not yet made habrarazrabotchiki. In the post there - in the comments not. Here is the script itself - userscripts.org/scripts/show/85482 . It will work in Google Chrome, Firefox, Opera, and maybe even IE8. Installation instructions, if you do not know how to install userscript, you can read here - at the bottom of the page.
The script works in both posts and q & a. It seems to contain everything you need and even irony . If you find any bugs - write.