I haven't tried this personally but for the last few weeks (and again today) I've seen people do it and it's always the same way :
-The link is always posted in a reply to a top comment. So it shows up as the last reply to that comment.
-It's always full of weird caracters like " Ơ " and has emojis in it. I guess that's so they can make lots of different comments easily and it also makes the comment stand out.
-The links are always "sites.google" links and the site redirects to a dating offer. But I guess you could create the site as a landing page not necessarily as a redirect, and obviously you could promote any type of products, but I've only seen dating offers for some reason.
Anyway that seems to work but I guess the accounts get banned pretty quick.