I was running backlinks analysis and it shown me some suspisious backlinks on forums. These links are natural, as users of these forums shared links with others.
Should I disavow such links in GWT?
You should keep them if:
If it doesn't harm you, don't disgard. Backlinks have value in Google, but quality over quantity, but a backlink is a backlink. Maybe it's not the most optimal place to get linked from, but if users click the link and visit your site, who cares? You just got a visiter :)
PS: Bing! goes with the quantity over quality logic, so that will benefit.