If you look for total category pages indexed of meta.discourse.org with following query in google
you will find 1670 pages index. Similarly i have a discourse site with 50 categories
while here more than 23 thousand pages are indexed under category. (A very very dangerous signal for seo because of content duplicacy)
It should be fixed otherwise google will penalise a discourse website rankings.
Look at the following screenshot how duplicate pages are created and indexed.