Can you post a screenshot of the sms screen so I can have a better sense of what exactly you are talking about. I thought the HTC messaging was left out of these roms but I'm not using the MaxManila rom so I can be certain of what you are working with. If you go to start/settings/system in there you have an SMS Threading Icon, once you click on it, it gives you an option for threaded or classic. You can try that and see if that works.
Here's the screen I have when I go to the "message" tab, (not the "email" tab)
And it's a BIG challenge to sent an SMS from this screen, in fact as soon as I tap on the contact logo to add a recipient the phone freezes...
Thanks for the help