The same crap is going around Instagram and other social media pages. Often when you check out the profiles, they have some link obscured via url shortener that resolves to some random porn site or flat out scam page.
They try to comment first to get upvotes I guess.
Blocking instances works with the OG Lemmy, but they didn’t build the function into the app, you’d have to go through the website (that one time only).
Or can you block all users of a specific instance with Voyager?