Please reread my response and the gtp-drafts carefully.
The overall design philosophy of GTP is: keep it simple, small and extensible. Only the commands that are common to all implementaions (those needed to make the program play a game) are standardised. Others can be introduced as an extension, and if they become usefull (and their semantics have cristallised ...) they could be added to a newer version of the standard.
It is perfectly legal to add private commands. The line-oriented protocol makes it very easy to ignore these commands.
Most programmers don't want to create/maintain a gui for debugging purposes. Too error-prone ... Most programmers don't want to support debugging commands (or their output) from *other* programs.
To me, the cheapest way to implement debugging is to just dump it to stderr (or a logfile, or both) For me, even fitting the debugging output into the GTP-format ( avoid \n\n ...) is too much work.
BTW please don't top-post. Don't cite the message entirely, without responding to it.
AvK