You mean you want to disable tooltips displaying post content within the forum itself? I guess for people viewing the front of your forum who don’t have access? If so you can disable this by adding the ‘tip=0’ argument to the function sp_ForumIndexLastPost in spGroupViewDesktop.php so it would appear:
sp_ForumIndexLastPost('tagClass=spInRowPostLink spLeft&tip=0&nicedate=0&date=1&time=0&stackdate=0&itemBreak= - ', __sp('Last Post'), __sp('No Topics'));
You can also do the same for sp_TopicIndexLastPost in spForumViewDesktop.php if you want to get rid of them from forum view.