I registered to the forum exactly for knowing more about this.
I love the game. I bought two copies of it to play with my girlfriend, and I want to thank the devs for providing us with so much "old-school" love. Thank you very much.
However this issue is making immersion and experience in co-op being pretty tough.
All we would need is for the second player to click the talking npc, and see a read-only version of the first player's dialogue window.
(of course it would be even better to be also able to talk with the same vendor at the same but that's definitely much less important).
I know the devs are probably super busy, and that we need to be patient, and I will be. But it would be awesome to have it soon

Anyway thank you again for making such a great game, good luck with all the hard work!