Well, that sounds like browser problem, not an OS problem. What browser are you using? Try an alternative one. If the problem is still occurring, post a screenshot of what happens after you click the "Reply Thread" button.
Opinions are like nipples, everybody has one. Some have firm points, others are barely discernible through layers, and some are displayed at every opportunity regardless of whether the audience has stated "I am interested in your nipples" or not - David Thorne