Awesome, thanks @codinghorror! I’ll share the audit here next week, in the order that we think would make sense to tackle these, and then try to get a first improvement done in the next two weeks, and then go from there. 
re: <b> and <strong>, the accessibility experts I work with included this in the prioritized list of changes recommended from their audit, so for them the change is meaningful I’ll find out more about why and include that in the write-up (I assume not all screen readers respect <b> but I don’t actually know). This is also why it’s so helpful to have input from you and other Discourse folks so that we can find the right tradeoffs and track down those details like the style rules that would be impacted when submitting PRs.
Thanks again for your openness!