Standard for BGP community lists

[Steve Bertrand <steve () ipv6canada com>]

Many ISPs publish community lists that go above-and-beyond standard
route selection.

Is there a standard for this?

ie. I want my clients to utilize my s/rtbh setup as they see fit, for
themselves. I'd also like my upstreams to do the same if necessary.

Is there a consensus on which communities are used for these purposes?
If so, which ones?

otoh, is there such an engineer/network that has a client that they
trust so much that they'd enable them to null a block for you globally,
via community list?

Steve