I wouldn't consider any links bad but low-value links instead like blog comments, social bookmarks & forum profiles

Profiles are definitely bad links. Sending enough of them to your site will make it drop like a brick.

Google doesn't consider unrelated links as bad (totally) links. It still depends on the quality of the page that you are linking to. In their webmaster guidelines, they have stated that we should avoid linking to bad neighborhoods. They didn't emphasize any specific type of links.

If irrelevant links are bad in the eyes of Google, you wouldn't surely dare to put a signature with a link back to your health care site here at WarriorForum.

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