> On further investigation, it seems the group config parameters "presenter" and
> "wildcard-user" interact in a non-trivial way.

There are two syntaxes for Galene group definitions: the old syntax, based
on pattern-matching, used in Galene 0.8 and earlier; and the new syntax,
based on a straightforward map from usernames to user descriptions, which
was introduced in Galene 0.9.

Galene still parses the old syntax for compatibility reasons.  You're
mixing the two syntaxes, which is confusing.  Please don't do that.  The
following fields are now deprecated:

  - "op", "presenter" and "other", replaced by "users";
  - "allow-subgroups" and "allow-anonymous", no longer supported.

> Having "presenter":[{}] seems to act like a wildcard user authenticator,

Yes.  That's the old syntax for what is now

   "wildcard-user": {"password":{"type":"wildcard"}, "permissions":"presenter"}

The new syntax is more verbose by design, so that you don't open your
server by mistake.

> unless another "wildcard-user" field is present.

If you mix the two syntaxes in contradictory manners, the new syntax takes
precedence over the old one.  There should be a warning in the log.

-- Juliusz