9:23 AM PT -- Donald Trump just addressed after his court hearing this AM in DC -- and it sounds like he might've not been made aware of this troubling hot mic comments ... just take a listen.

DT said that while he was dismayed by the case and the charges in general -- continuing to insist he's getting railroaded over politics -- he did thank the media for covering this one "fairly." Of course, what the journos were joking about out there seem to indicate a slant.

That's putting it lightly ...

Covering Donald Trump's arrival at a federal court is hardly the time or place to be talking about assassinations, much less making jokes about them ... but that's what 2 journalists did, and they got busted on hot microphones.

The 2 unnamed journalists were outside the E. Barrett Prettyman Federal Courthouse Tuesday morning in Washington, DC -- waiting for the former president to pull up -- when they started assessing their position and whether they'd have a good view of Trump.

Apparently, they forgot where they were and what they do for a living ... because with open mics all around they start joking about Trump possibly showing up in a convertible -- a la President John F. Kennedy in his ill-fated Dallas motorcade on Nov. 22, 1963.

One guy says to the other, "Maybe someone, just like they told JFK, 'Y'know what ya should do, you should take a convertible!" Hahaha.

The video shows police officers standing just a few feet away from the mystery journos, but it's unclear if the cops heard the remarks. It's certainly possible the Secret Service will take an interest in the video.

Trump showed up at the U.S. Circuit Court of Appeals -- in a motorcade of SUVs, for what it's worth -- to argue he should have immunity from prosecution in special counsel Jack Smith's election subversion case.

While the journalists were clearly joking -- it's the kinda thing reporters do while passing time at major events -- this kinda humor never sits well with those protecting Presidents ... past, present or future.