[tertius]

I don't think the President should be hindered by a private company to do his job. Whether we agree with how exactly he's doing it or not.

The TOS is clearly based on law, it's legal for him to do it, so in essence the TOS regarding to his legal rights, shouldn't (in spirit) apply to him.

Now if he was doing something that he doesn't have the right to do, i.e. inciting violence against a private person, he'll break the TOS.

If all you want to say is that what he has done is strictly against the text of the TOS then sure I'll agree. But I don't think it matters.

[Retra]

The president hardly seems to be "doing his job" on Twitter.

[tertius]

I honestly don't think my or your opinion matters with regards to that.

If he tells a foreign official anything at any point in time whether it be email, phone call, twitter etc. it's official. He can't claim that he was taking a break. He can delete a tweet, but that doesn't mean that it didn't happen.