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Consensus among witnesses and a hard fork.

I would be ok with 100% HBD payouts but feel they should come with a fee - 1% burn to get your posts fully liquid. Thus, you get a (very) small bonus for accepting vested rewards instead of fully liquid.

Edited: doesn't appear to be active

You can already do exactly that with the @likwid service. Of course it is not built into the chain (and doesn't increase HBD supply) but from the end user perspective, same thing.

Doesn't look like it's active anymore, there's another service myself and @cardboard created which has that function as well that I mentioned in a comment here but yeah it doesn't increase HBD supply.