Witness checks include data about the node in
place at the time that the witness even occurred,
so players are not awarded credit if the node they
see there was changed again afterwards. A lot of
old witness code inserted the witness right
before the node was changed, since the node
change was done as a tail call, but this does not
work with delayed witnessing because the
delayed witness data would be tied to the old
node, not the replacement one.
Moving witness to after node setting should fix
a number of broken hints that should have been
delayed-witnessable, e.g. brick bonding.
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