To make the Toolbox look better and more consistent with the rest of
GIMP. I suggest that the "You can drop dockable dialogs here" be
dropped and the Toolbox Widgets be forced to the bottom leaving room
for dialogs to be docked at the bottom of the tool box.
This label is not really needed as when users first start up GIMP
there is already a dialog underneath the toolbox so right off the get
go they know that you can place dialogs here. If the user decides to
take this dialog and place it anywhere else, now there is this ugly
label telling them what they already know they can do. This may even
be insulting to users, as you are saying they need a big banner to
tell them how to use your software.
I'm sorry but there are no "insults" in having a label giving information to user (what about status bar, tooltip bubbles, or help button and doc pages! They all give information on how to use the software, hence would be insulting? Seriously?). This is a non-rational rhetorical method which one can indeed see in some bug reports saying basically "if you don't do this change, then you are insulting users, therefore you are assholes; so you have no choices and do what I say". And I wish not to see this kind of things on this mailing list, please.