I have a WordPress blog(blogging and technology niche) with 10,000 monthly SEO traffic(95% from Google). I have decided to add forum using bbPress to that blog(mydomainname.com/forum). I can't maintain a high quality content on forum. Yes, I can remove spam posts. But still their may be lots of thin low quality content on forum. So it can hurt SEO traffic? Will it lose current SEO traffic also?
Inclusion of forum page within a site will not hurt your SEO. This page will attract more visitors to your site because most of the visitors prefer active online community in the site.
Anything to promote discussion is a good thing. A lot of new visitors will discover your site through the forum if it gets popular. Just make sure you properly manage the community.
when good discussions really get going and new information is discovered or revealed then other people, especially bloggers or people on other forums will link to it naturally. These organic links will really begin to add up and create much greater domain authority for your site.
It won't hurt you. Forums have thin content in nature. Google knows that. You need to make forum spam free. Forum helps user experience and it attracts more traffic. So forum may help your SEO.