Instead of completely disabling 'Interacting [F]' while on Mounts, how about having NPCs automatically 'Stealth' nearby Mounted players, and only Mounted players, within a radius (being completely invisible instead of otherwise transparent) in the event too many players get too close to any NPC? whereupon an 'Effect' icon pops up just above your Skill Bar that says, "Other Mounted players nearby NPCs are hidden except you to prevent crowding." and then call this Effect something along the lines of 'Hiding the crowd'.
The radius around each NPC (or only important NPCs, however Anet goes about it) would be this big: https://imgur.com/a/T4P3f and any other players within that circle other than you are seen as hidden, yet with player names intact.
I also want to make very clear that other Mounted players you see who are hidden (as a result of coming within the vicinity of NPCs who are under the 'Hiding the crowd' Effect) will still receive damage from enemies near NPCs. Therefore, just because the player (you) cannot see hidden Mounted players does not mean enemies cannot see those Mounted players. You can't see them, yet enemies can see them.
Player names, however, will still show as they do when in Stealth, yet player names can be turned off in the Options Window.
Does anybody have a better idea? If so, let's hear it.