Hi, I saw some marketplace offers to buy do-follow backlinks from Reddit. Is that something I can fairly-easy create by myself? Also, are these links even beneficial for SEO? this comment on Quora talks about the implementation of rel=noopener & rel=noreferrer on Reddit, but I'm not sure how it affects the link juice. Thanks!
You shouldn't just focus on do-follow links the end goal is traffic and a natural backlink profile will have both do-follow and no-follow links.
They are beneficial at least because you want a diverse link mass (no-follow, do-follow, sites, forums, etc). I have a reddit account and my links are definitely do-follow and I am not an advanced member or anything. According to John Mu rel=noopener & rel=noreferrer does not affect SEO and links with such parameters are just links. So, I would not be worried if I were you.
You need to post a full post to get a dofollow link on there. Many people also sell them. Also, focus on the traffic you can get from the post, so make it amazing and you'll get tons of traffic. Post a crap article and you'll only get a link.