Without further modifications to the interpreters and GLK, currently the only way to pass messages through the parser to the browser is to hack in to some pre-existing method. I used the left status line for my experiments, but that caused some problems in downloaded files played on an interpreter. Vorple instead hacks the save system, I believe, and possibly the transcripts. So that’s probably why it’s not showing up, as I believe the channels you’re used to using have been co-opted by vorple.
From another thread: