Re: member activity page on specific activity is TOO barren (help)
Yes, BuddyPress would definitely benefit from a serious UX review. Theming is much harder work than it should be. It’s far too tightly coupled to the core, with too much presentation code / decision making embedded and difficult to change. The permalink activity pages are definitely the worst presented and often most useless aspect of the default setup.
That said – the default setup can never be made to please every user. It’s perfectly reasonable / normal to have to create and modify your own bespoke template files to get the site you want. It’s the same for WordPress, Drupal, Expression Engine – any content management system you care to name.
Copying everyone under the sun on your post, is unlikely to win you many fans! However, there really should be somewhere more obvious and accessible to raise thoughts about the interface and BP experience.
My tuppence worth: make the API much finer grained (e.g. accessing the activity stream elements by part, rather than monolithic string), loosen the presentation coupling as much as possible, and put out a default theme that’s based on a finer grained access, and therefore much easier to understand how to re-work and restyle. This would encourage more theming, more unique uses of BuddyPress and push the boundaries.