“-” is the default delimiter in qmail. I administer a system, where both + and - are valid recipient delimiters for historic reasons and we can’t really get rid of it.

Believe me, it has caused all kinds of problems, where we have to go deep into the finer differences between aliases and virtual aliases and transport maps in postfix to route mails correctly. Especially since we have a lot of Mailinglists with - as a valid character in them.

So to summarize: the assumption by changeorg is valid, however the execution seems rather flawed.