Running WAVE on Discourse hosted reveals a handful of WCAG accessibility issues.
Posting each in a separate #ux thread.
Hopefully these are repeatable using WAVE on your own instance, but if not I can provide details on any of these items.
For the homepage:
|Issue found||Guideline||Found by||Notes||WCAG Level|
|Empty table header||1.3.1 Info and Relationships||WAVE||table header contains no text||A|
|Image with title||1.1.1 Non-text Content||WAVE||5 instances||A|
|Missing first level heading||1.3.1 Info and Relationships||WAVE||A|
|Redundant title text||WAVE||Not sure if this is discourse issue, or with component “Brand Header Theme Component”|