I'm not a seasoned member, but I've some thoughts on this. I'll focus on practicalities rather than on accepted site policy.
Let's assume the aim is to give a permanent acknowledgement and provide a link—which would seem to be good practice with online material in general. A matter of courtesy and acknowledgement of sources.
As to where to link, I can see some potentially conflicting considerations.
- If the link is to a comment, the comment might be subsequently deleted once it's done its job of helping you. So the link won't be valid any more. A profile link is likely to be more permanent.
- If the help was spread across a number of comments or posts, it might not be practical / sensible to link to them all. A profile link has the benefit of being a single link.
- But linking to a comment enables readers to see what the help was, which is more informative—if they want, they can then click the commenter's name to see the profile.
- There might be people who prefer not to be linked to for one reason or another, especially if (for example) they're having trouble with trolls etc. Or maybe if the post is unexpectedly controversial and they don't want to be dragged in by getting heated replies to old comments.
When I'm reading, is the presence of a link problematic? Only if it's unnecessarily obtrusive, or leads me to think it will go somewhere more interesting than it does. But it's obvious that if someone's name is highlighted as a link, I'll most likely be taken to their profile page or possibly their website.