Credibility or link value? Your sig area.
If you use your sig area to fill it with links that all go back to the same site but using different keywords - you put a big negative weight on the value of your posts.
Not everyone will see it like this but many will.
If you waste your forum name by making it a domain name and fill your signature area with spammy looking links, it comes across that you're just here to abuse the value of the forum for your own purposes and you're not here as a genuine member looking to be part of the community.
Even if your posts are good and thoughtful - your sig area makes it look like you're just posting to get your links exposed.
There's no problem at all with linking to your site(s) from your sig area but when you fill it with a bunch of links to the same site it just looks desperate and you may not realise the impact it has on people's perception of you.
So, if you're about to create an account and were thinking of using your sig area like this - please reconsider.
This forum is amazing and there's a lot more value to be had from building relationships than link spamming.
Andy
Founder of JVZoo. All around good guy :)