I don't think it's all-right in a design whose explicit set of goals include
"People not from tails@boum.org shouldn't know how the shares are spread and who
has them".

List subscribers risk replying to the list instead of (or in addition to) to
tails@, which would violate "Unless you really want to start the key revocation
process, do not write to this mailing list".

I'd rather not rely only on a big fat warning to avoid that, while we
have a simple solution to lower the risk significantly.

This reverts commit e593db47.

This second vulnerability might be harder to exploit without the first
one but its consequences could be as bad.