There was some discussion in #bitcoin-dev about signaling non-listening nodes too but the problem is that nodes can't currently tell if inbound connections work. Some logic can be added to request peers to try connecting before deciding that you're listening and announcing, but it's more than a few LOC...
The general idea was that nodes would wait some amount of time (we only really care about high uptime nodes listening) then request some of their peers to connect to them. If it works then they advertise themselves as listening. This doesn't just matter for IRC but also for the peer requests over the p2p protocol.
It didn't sound like anyone had committed to writing that yet.
I think it sounds like all of these things (incl. DNS seed and the other stuff in the linked thread) need to happen eventually, but fixing the connection timeouts plus anything else is enough to meet the urgent need.