In practice, there's often no useful difference between a thin cloud of vile-smelling smoke and a thick cloud of fruity-smelling vape: many people would prefer to avoid both. (Also, the vape cloud leaves much more residue than smoke did, just much less foul). Best policy seems to be to use the things only where actual smoking is allowed to try to avoid annoying bystanders.

I wonder if people would still be annoyed if it didn't produce a cloud?

To me, it seems like many people have this weird "ick" about natural biological functions. Some are understandable - like body waste, and sneezing/coughing that could spread contagions. Regular smoking I can understand from the standpoint that it smells bad.

But vape clouds typically smell good. But they are visible. So people are reminded of "ick - breath!" meaning something similar to coughing/sneezing (and not covering your mouth/nose)...

Yet, nobody seems to have an aversion to everyone around them just "breathing" normally - or even an exasperated sigh or huff - which is arguably just as much breath coming out as someone vaping.

Just that it is invisible - and now no "ick factor" if you will.

It's kinda crazy; here is something that can and could really help smokers, yet being vilified because of some weird hangup people have with breathing - because it is visible. It is similar to how some people love to eat chicken nuggets, but give them a bone-in chicken wing and all of a sudden it is "gross - it has bones" - like the nugget is somehow more sanitary or further removed from the chicken because it is boneless?

/humans are weird

Vape clouds smell awful. Like all the artificial flavourings I dislike, applied the way a 13 year old boy applies deodourant.

If it's rude to spray perfume or eat smelly food, then it's also rude to vape.

No-one is saying it's not rude. What we're asking is whether it should be illegal. And your own comparisons suggest that it shouldn't be.

On the other hand, it's a big thick cloud of vapor coming from someone's mouth.

What about a thick cloud of... carbon dioxide and water vapor, from the people standing around you?

...which is difficult to perceive unless they are close enough to be obviously breathing on you. Or have bad breath. Neither of which is appealing.