Comment 1 for bug 266187

In general, Mailman's philosophy for member addresses is
case-preserving, case-folding, meaning that <email address hidden>
and <email address hidden> are considered the same member, but if
they were subscribed with the former, we will send the
message to the former.

I think it's valid to extend this philosophy to
acceptable_aliases, and so I think the right thing to do is
to treat an alias such as <email address hidden> the same as
<email address hidden>. I will commit a change that adds the
IGNORECASE flag.