I figured since this was a community named Test this was a fitting place to test this. I didn't expect such a quick reply though at all before I get the chance to delete most of those. 😀
I've just set up a Lemmy account for this specific purpose now, but replies and notes seem to work fine from Mastodon.
Test all the things, I say! (It's a weird habit I have to always comment on them, TBH.)
In reality, all people need to do is block the community. Because Lemmy is a bit small still, it makes sense that people browse /c/all, like me. Unfortunately, browsing All has the downside of more spam and floods of test posts at times. (Still, it's a good lesson on how posts propagate.)
The worst was one instance that was replicating posts from Reddit, with bot account copies of users that were commenting on Reddit. (It was supposed to be a way for users to "migrate" to Lemmy, but turned out to be spammy as all hell.)
It really gives some insight, I was surprised how quickly the posts showed up on Lemmy! The bot sounds very much like why it was considered a bad idea to have a server converting Twitter posts in real time to the Fediverse when the API still was economically accessible lol.
@MIDItheKID Ah, sorry about that. I was specifically trying to trigger Lemmy to detect it as just a link, and not a note. But does not seem to work. Thanks anyways!