Replying to Adding subject line to buy/sell messages

I often sell multiple pairs of goggles, skis, etc. and I usually get responses saying "are these still available" in which I have to then ask which item they're referring to. It'd be nice if when messaged from someone in the buy/sell section that it comes with some sort on info receipt or something. Heck, even just adding subject lines to all messages would help as well like seen on TGR or Pinkbike (would be pretty easy to add that under the username in the inbox column)