No. Of course not.

This question feels like a dog-whistle.

It’s not a crime or anything. I would definitely assume they have some sort of developmental issue though.

Context matters here.

A teenager with profound mental disabilities or one who expects to be get a job in the future?

Also, long term thumb sucking can impact dental development. I knew a kid who had to have braces for years because they kept sucking their thumb until age 10.

Unless I’m the teenager, it’s none of my fucking business.

Only during sex. /s

It’s a fucking free world. On the other hand, it is definitely good if a psychologist appears on TV, and explains the risks associated with such behavior; teenagers are little rebels, and an authoritative person telling them to stop doing something is good for their development towards adulthood, albeit it will guarantee that they will suck their thumbs even more. If you want them to stop sucking their thumbs, join in, and start sucking your thumb as well. Within 48 hours they will need to look for something else to upset you; which, interestingly is equally important for their development towards adulthood.

Depends, are they biting their thumb at me? Might have to pull out my rapier.

Do what you want, but pretty unhygienic.

Okay in relation to what?

Socially speaking, people will look at you weird.

Hygienically speaking, a bad idea as constant moisture etc. risks both bacteria and fungal infection.

If you touch things that other people touch with saliva in your hands, you might run into some trouble because again, it’s unhygienic and most people will think it gross.

If you’re cool with all that, you do you but other people don’t have to be cool with you doing that.

An important aspect of teenage life is the social aspect. Every teenager wants/needs to belong to a group of peers. It is quite literally the primary drive of the average teenage brain. This is how humans learn to live in groups since the dawn of history. Sucking you thumb in public will likely, negatively impact you social status among your peers and is therefor naturally discouraged.

On the one hand it is okay to be you, but on the other hand you need be very steadfast and confident if you’re going to withstand teenage social pressure for something like this.

I sucked my thumb until about 18, but only in bed. Than I got a girlfriend. We quickly moved in together and slept in the same bed. She knew that I sucked my thumb, called it cute and didn’t make me feel awkward about it. However, I practically couldn’t wrap my arm around her and suck my tumb at the same time, so that’s how I stopped doing it.

No

Im going to say no for two reasons. Firstly its bad for ones teeth. If someone needs to feel the need to suck their thumb they are likely going to do it to the extent that its bad for the teeth. Secondly the social negatives will be massive. Bullies will wing off almost immediately and there is a good chance of having some sort of physical altercation. Unless your built like a line backer. Maybe then you can be so physically impossingly powerful to keep bullies silent. Beyond that though its likely to negatively impact various social situations if a schoolmate or work mate sees you. Heck it could follow you into some adult life interview. Its just to outside the norm.

If you need to suck your thumb as an adult, get counseling. I don’t mean it in a bad way, you have legitimate underlying issues that would probably be helped. You’d feel a lot better in general probably.