|Glass door with vertical handle|
Often, as with other kinds of doors, the person in front of me will try to hold the door for me even after they've taken their hand off the handle, by putting their hand on the glass part of the door.
The problem with that is it leaves fingerprints on the door, which some poor cleaning person will have to clean off!
Barring extenuating circumstances, cleaning fingerprints off glass is far harder than opening a door! By holding open the door with your hand on the glass, you're making a net negative contribution to other people's ease and comfort, not a net positive contribution.
Therefore, I propose that putting one's hand on the glass of the door should be considered rude, and doing so in the course of holding it open for someone who is perfectly capable of holding it open themselves should not be considered polite enough to outweigh the rudeness.
(Holding the door for someone who is genuinely unable to open the door because their hands or full or they're not strong enough or something is polite enough to outweigh the rudeness, but we should nevertheless endeavour not to touch the glass.)
And if you really feel that you would be perceived as rude if you're not seen holding the door open for someone, all you have to do is keep your hand on the handle for as long as possible as you walk through, ending with your arm stretched out all the way (and perhaps looking expectantly back), like this gentleman.
(Although the optimal way is still to be completely on the outside of the door, like this gentleman.)