There have been cases of US deportations for even having US critical posts in your feed without making them.

https://www.thecrimson.com/article/2019/8/27/incoming-freshm...

https://techcrunch.com/2019/09/02/denied-entry-united-states...

Eh - I knew Arab students who couldn't get their visa renewed for some years after Sep 11. They were involved in antiwar protests, etc. The fact that the US put many of its own anti-war activists on no-fly lists despite not having any evidence they were threats makes this pretty easy to believe.

There are plenty Chinese students unable to renew their visa to the US for 'national security' reasons.

Right, but is there is any evidence that any PhD student has ever found it hard to get a US visa because of criticizing the US or US policy?

Border control / consulates check social media profiles, a policy implemented by Trump, I wonder why.

I wonder why...

https://en.wikipedia.org/wiki/List_of_Chinese_spy_cases_in_t...

https://en.wikipedia.org/wiki/Chinese_espionage_in_the_Unite...

Is this close enough: https://www.universityworldnews.com/post.php?story=201908301... ?

Happy ending here: he was admitted to the country a week later, on his second attempt, in time to start classes.

(I'm not making excuses for the---dire---state of our immigration policy as a whole. But I was happy to see that this particular case worked out in the end.)

Wouldn't asking for all your social media identities as part of the visa application create somewhat of a chilling effect?

That's the idea, I would guess.