I'm not a fan of having tags per product (aside from the top level ones, of course), so sqlserver-listener is a non-starter for me.
There does not appear to be any crucial difference between an Oracle Net Listener, and any other sort of Listener, so it seems unnecessary to create ag-listener, especially since listener only has 47 questions (21 in the past 12 months).
It would seem better to edit the existing listener wiki and excerpt to be more generic, covering all types of network listener.
There are no listener questions (except the one mentioned in the question) that are not already tagged oracle, so no information would be lost. The subject question would then be quite happily tagged as-is:
Update: Based on the feedback, I have edited the existing tag excerpt and wiki.