Oh, I remember Moxie claiming that they've built Signal as a Chrome app because Chrome has won the desktop: https://news.ycombinator.com/item?id=10665679 - I can't decide whether this is funny or sad.
I like Signal, and I depend on it, and wan't it to be successful, but oh boy are people running it full of misplaced hubris. A lot critique is dismissed just like in the thread you link: “we wan't to stop mass surveillance”. “But Moxie, change X makes Signal less useful/less secure for a lot of people who really need it!”, “We're glad you're an irrelevant geek, but we wan't to end mass surveillance”... Implying they're making Signal approachable to “masses”. But they aren't, partly because proper security will never (for various values of “never”) be approachable to disinterested masses, and partly because they pull some ideas on usability out of their ass.
Feel free to keep using the wonderful pgp user interface.