Recently, I've found that the click on horizontal scroll problem that was fixed with patch #3134788 has resurfaced.
I tracked it down to a change in the behaviour of my JRE, which has apparently started sending horizontal scroll events as mouse button presses with button numbers 4 and 5. (Such numbers > 3 are documented to be allowed with Java 1.7, so this probably started after an upgrade to that.)
Since the original patch (and the current trunk) simply checks for the event's button being MouseEvent.NOBUTTON, these "clicks" are not caught and suppressed.
This patch replaces the check for NOBUTTON with an inverse check for BUTTON1 or BUTTON2 or BUTTON3, since those are the buttons that jEdit currently knows how to handle (as far as I know).
While it would be better to handle these "clicks" as scroll events instead of suppressing them, I don't know how to do that, and I don't know how universal the 4 and 5 would be either - so trying to do that might be trading one problem for another.