Well, we’re effectively already forked it, as we had to remove infinite scrolling and add normal pagination (took 2 days to implement, while some Dev on this forum stated that this would take 2 months); customised the url structure to fit the needs (which was actually PITA, as someone not really smart obviously hardcoded all the routes in JS as string instead of using EmberJS routing mechanism. Had to search and replace tons of strings); hacked the routes to handle more than 2 levels of categories; So… Yeah, I’d say “forking discourse” is not a big issue right now. 
And no, you’re wrong, I like Markdown, but this is a task from higher in the hierarchy and not something to discuss.
PS. I’m starting to think that picking Discourse was a bad idea after all - it’s really PITA when it comes to customisation and tweaking.