Wow, the delay is real LOL I replied from Mastodon but it hasn't shown up here so I'm replying from vger.app and will see what gets here from where and when :-D It's cool that it's possible though, even if it's not super practical.

EDIT to say that this comment showed up on Mastodon basically immediately but my Mastodon comment still hasn't shown up here 1-2 hours later?! Weird??

@60d Nice, so it definitely works but there is quite a delay so not perfect. But here I am replying again from mastodon after checking that it did finally show up on Lemmy!

the way I do it is open up lemmy on the browser and you can copy the fediverse link and paste it into mastodon to search for it, but federation is a whole thing so not everyone who sees something from their instance sees everything from every instance depending on who is federated with who, so with mastodon and lemmy it gets a little weird. Ive seen some tools that help pull more content that otherwise your instance wouldnt automatically get itself so that you can see more replies etc but I havent messed around with that

@sqgl Apparently not. I just searched for their username on Mastodon, saw their comment and hit reply. I noticed later that Mastodon does have a note below the comments saying something along the lines of All replies might not display, go to Lenny to see more.
EDIT to add that this time, this reply from Mastodon showed up immediately on Lemmy 😂

@60d
Yes!

I just "favorited" it and clicked reply. I believe the reply shows up as a reply, and the favoriting action looks like an upvote.

It's kinda silly. Like... is this useful? Unclear. But the ability for me to interact across two very different platforms seems like a technical achievement to me.