I recently merged my multiple bbpress forums in a single Discourse Forum, Google is indexing it very very slow. It can not go very deep.
From one month i am getting 200 pages per day get indexed, while usually a new content get indexed to 0.1 posts in a month. Its hard for google to index a big forum.
Following three things must be solved so that discourse can be use for multipurpose sites.
dofollow, noindex in header (meta- robots) of the tags pages. Forum with too many tags will create too much Duplicate content in index without this solved.
there must be a way to edit the robots.txt to include sitemaps, or to avoid unnecessary pages get indexed.
There must be a sitemap facility, just like nodebb.
In nodebb all of these three things are possible. but i used discourse as it is more stable in big databases.