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The /forum route only works on tags specified to match a forum that I've created, and I haven't made one for gridcoin yet.

However, the topics interface will let you do that:

https://beta.chainbb.com/topic/gridcoin

I need to make that easier to find, just haven't got around to it yet :)

Ah cool, good to know. The site looks great, good job! :)

Thanks! Was actually a lot of fun to build, and be able to re-envision steem as something besides just a blog :)