Yeah, links are delicate. I see no problem if it’s a relevant link to a third-party that you don’t benefit from (e.g., a link to a Wikipedia page). If it’s a relevant link to one of your own articles, well, then it depends on how you have justified linking to it and whether it really is sufficiently relevant.

But if someone just pops some blatant spam into the comments section of one of my articles, I will not only block them, but also report them.