I think this is probably a big part of it actually. If you're inserting emojis you're probably on a phone, so you're probably interacting with the discussion in a quite different way than if you were on a PC. It's not as comfortable to write longer, better-thought-out comments.

People pick up on these implications and judge people accordingly.

On Windows, it's Windows key + .

On Linux, there's an app called Characters to copy paste emojis from, and some apps use custom key combinations such as Super + ;, or Fn + ;, or something like that