For many years I used this custom forum software to host discussion about SumatraPDF.
Unfortunately recently spam became much bigger problem so I decided to move the forum to a hosted platform, which hopefully has good anti-spam technology.
New forum is now at https://muut.com/sumatrapdf#!/
New forum is a bit shinier, has more formatting options, allows updating images etc.
The downside is that it now requires logging in to post but that's the unfortunate reality of a world full of spammers
Soon I'll disable ability to post new topics or reply to old topics.