Yes, I can confirm that Jom Classifieds is not compatible with T3 framework. I have installed T3 with Purity III template. Jom Classifieds seem to mess up fonts of the hyperlinks.
Jom classifieds team - you need to fix this. Your standard answer seem to asking for the admin/password of customers' websites; I would ask you to focus in fixing the issues rather than customizing your scripts for each and every customer.
Also, you need to provide simple mechanism to allow customers to change layouts of your standard pages such as 'add ad page', 'my ads page'. What you have done is a good start but every country, every culture and regional settings demand customized approach for these layouts rather than what your programmers have 'coded'.