Should be listtransactions with s.

fixed

This paragraph doesn't really make sense when both behaviors are present in the same release. I'd maybe change it to:

When bitcoin is configured with the -deprecatedrpc=accounts setting,
specifying a label/account/dummy argument will return both outgoing and
incoming transactions. Without the -deprecatedrpc=accounts setting, it will
only return incoming transactions (because it used to be possible to create
transactions spending from specific accounts, but this is no longer possible
with labels).

I think it'd be good to document the empty string change. Maybe:

Also for backwards compatibility when -deprecatedrpc=accounts is set, it's
possible to pass an empty string label "" to list transactions that aren't
labeled. Without -deprecatedrpc=accounts, passing the empty string is an
error because returning only non-labeled transactions isn't actually very
useful, and can be confusing.

Both are good changes. Thanks!

I don't see how the new check for "*" here changes anything. Maybe drop for clarity (unless I'm missing something).

No, you're right. It's better without. The behaviour would be identical with or without the check for "*". I've removed it.