If you push the "X" key while mounted you are overrated and probably gay.
Cuz you can't just downblock them, or have your horse beast 10 of their thrusts?
If I see a 2h'er on an armored horse, I pretty much only try to couch them. If they are a lancer on armored horse I don't, because I don't want to get outreached, but I'll still aim for their horse unless I see they are open to me hitting them. Nothing more frustrating then having a clear shot at someone (or their horse), you go for the person and get blocked. Especially so if they dismount or kill you from their horse later in the round.
That's pretty much the only time I couch is versus heavy armored horses, or a shorter 2h or polearm that I know will just downblock me every time I make a pass.