This is a great example of a "feature" that seems to make sense but, for reasons I can't quite put my finger on, really bothers me.
Maybe it's that Discourse's search functionality didn't really work well, or suddenly started searching across threads rather than only the current one (IIRC); maybe it's that it's the only system I can think of (other than google docs) that hijacks the shortcut, but it gave me a very negative first impression of the tool.
For another similar example, the Blendle website (note - not the app!) hijacks Esc when reading an article, and interprets it as a shortcut to return to the main page of the site. I actually reported it as an issue to them, and they said it's by design and not going to change. :/
Maybe it's that Discourse's search functionality didn't really work well, or suddenly started searching across threads rather than only the current one (IIRC); maybe it's that it's the only system I can think of (other than google docs) that hijacks the shortcut, but it gave me a very negative first impression of the tool.