I'm not following it because it's illogical. You said, "No one has a First Amendment right to speak directly to the President. No reporter has an individual right to be granted an interview by the President."
I'm on Twitter and UNLESS TRUMP BLOCKS ME, takes an affirmative step to exclude me, I DO have a right to comment and join others in discussing his public statements about official U.S. business that he announces on Twitter.
I don't think you understand how Twitter works. I've got maybe 50 followers, so when I comment on POTUS that's my entire audience - the ONLY people who will see my comments. If I respond to @POTUS or @realDonaldTrump, 100s of thousands at least will view my comments, and I can engage with those same 100s of thousands in public discussion. You're asserting without argument that doing so is a "de minimis" inconvenience, but that's objectively FALSE. It's not an inconvenience at all - it's a
ban from that public forum. The only way around that
ban is to pretend that I'm someone else and post under another name.
Furthermore, that ban significantly affects my ability for others to hear my views, and it's a restriction imposed by government.
The analogy is it's OK for government to censor, block me, from using public forums A, B, C, D and E, so long as I can still access public forum X. Or, alternatively, the government banning me from speaking on the actual public square because I'm critical of that same government but contending my rights aren't violated because I CAN speak in the back of a nearby alley by the dumpster.
Up until this comment, you've ignored the restrictions on my ability to comment and participate in discussion on Trump's feed. So you've not addressed the issue at all except with hand waving the issue away.
Again, if you understood how Twitter works, you wouldn't ask that question. @realDonaldTrump has over 30 million followers. If he blocks me from his feed, I cannot reach that audience by commenting on his tweets. It's a significant restriction on my free speech rights.
Ad hominem. Great....
But if you want to go that route, an appeal to (your own) authority, this guy who has handled hundreds of cases in front of the appeals and Supreme court thinks you're wrong:
https://lawfareblog.com/blocking-twitter-users-presidential-account-0