Other ex-presidents have used the Great Seal. Trump altered it to make it look more like the presidential seal.
Ex-presidents have—but don't commonly—sign their correspondence "President."
Trump did both while on trial for falsely claiming he's the legitimate president.

Trump did the above after causing a stir for fraudulently devising an "Office of the Former President"—note the definite article—he later had to retreat from.
Trump is currently in a fight to break a contract so that what he calls the "Southern White House" can be his home.

One reason I'm a curatorial journalist is because this genre of journalism presents a clearer picture of events *and* their context. Simply saying Trump *can* use the Great Seal, or Trump *can* call himself "President," misses every piece of critical context for these actions.

I also wrote recently that Trump stole—per the NYT—his family crest, just as he stole Reagan's tagline Make America Great Again and then trademarked it. Trump has a history of trying to steal legitimate statuses others have earned/built—and he *will* do it with the presidency.

So those who normalize Trump by *robbing* his actions of their context are not more responsible journalists than curatorial journalists—they're less responsible. And their "gotcha" moments ("Other ex-presidents used the Great Seal!") come with a substantial cost for all of us.