Correct, you cannot use that method because the Latest Comments module isn't 100% MVC. As such, you'll have to manually edit the CSS and whatnot for the module, which isn't very flexible.
The only other thing I know about that's JoomlaComment aware is Super Activity, but I don't know much about it and don't know if it's similar.
I hope to make the Latest Comments module fully up-to-date so it can be dynamically styled depending on the itemid being viewed - it would greatly increase the weight and value of the JoomlaComment package as a whole.
I'll throw you a bone here. Unfortunately, Daniel is taking it easy for a while (Study, Work, BiggieSmalls, real life, etc) and while I am here helping take the load off his shoulders wherever I can, I am still learning the advanced concepts of Joomla extensions. So, I can't give a timeframe for this. I'll ask Daniel though if he thinks we could concentrate on this soon.
Don't forget - JoomlaComment4 is an incomplete Beta that is based on a Joomla 1.0 native component
we're getting there, please be patient! And of course, you are welcome to help us out in some way if you can