It doesn't hurt to ask!
Post Nov 19, 2016 10:59
Just found out this online mapping tool.
It's very similar to (and probably inspired by) Grid Cartographer, though much more primitive and not really a competitor.

However, one thing it does right is how it displays note tools.
You hover the mouse cursor over a map square with a note, and a text balloon appears.
It's a) nicely rounded and shaded, not just a rectangle, b) located right above the targeted square, not in the top left corner of the app.

Could you please incorporate these improvements into GC if it's not too much trouble? :) They are probably minor in terms of code, but they would be a nice improvement for map readability.