if it is possible; how do you do it?
no, impossible. But you can suggest feedback >> https://repl.it/feedback
Markdown accepts inline HTML, just use a element.
you can't. Something close to that would be gifs. But only images work. Not videos.
you could suggest to feedback.
you can't. You can only upload images.
This tutorial is everything repl.it supports: https://repl.it/talk/learn/A-Quick-Guide-to-Replit-Talk-Markdown/7448
why do you need videos anyways?
I've tried before but I don't think they upload, you can upload giphs though I think
So technically you could convert a video to a giph and then post it