Just shipped tip forwarding on posts ...
  1. It's hidden in the options pane
  2. It's 100% only
  3. can only forward to SN users
It's pretty basic support but I'll refine it over time.
All the other schemes are too complicated to start with - sending 1 sat at a time to lightning addresses is not simple. If lots of users end up forwarding, we'll refine it, but I suspect it'll see limited use.