In reply to GJ.

@Steve I think it's worth noting that the projects you mention are developed by different people:

bbPress, BuddyPress, and the upcoming WP REST API are all community projects; if you're interested in one of those projects you can join them and help with developing, testing, or documenting. For the people contributing to those projects, I don't think it's a question of prioritization; they contribute because they like the project and would like to bring it further. That's how WordPress works!
The WordPress.com interface and the WordPress.com desktop app mentioned in this post are developed by Automattic, the company making WordPress.com, and consequently prioritizing WordPress.com ?

I don't think there is any work being done to improve WordPress' commenting system, though. If you're interested, do not hesitate to start looking for people who would want to help with that, and start working on a Feature plugin that could be merged into WordPress Core some day!