IMHO it would be better to see what kind of extra libs/plugins are loaded without debug level (it's easy to forget that you have this maybe-buggy thing in your path). I'd vote for posting those by default.
i'd do a gui-plugin that raises the debug-level.
That's always a possibility, you can set the default debug level with a one liner like:
set ::loglevel 4
As for what should be the default behavior, that's a tough question. I've heard from a lot of newbies that having lots of text in the Pd window at startup is quite intimidating, so I think its good to really only show errors and strong warnings by default. More advanced users can hopefully figure out how to set the log level.
I see gui-plugins more like "add-ons" and seeing that some of them behave strangely, I think it's a good habit to have infos about external libs being loaded in default debug level.
from a noob pov it could easily lead to problems such as:
this kind of infos posted at startup would make sense to me: Gem version x Gridflow version x xxx-plugin version x ...
but maybe that's just me ;) I understand your point though and I'll remove it from my code.
cheers, _y