from https://bugs.debian.org/787690:
using pinentry-gtk-2 0.9.3, typed passphrases > 32 characters return an "OK"
response with no pin.
I've tested with 0.9.2, and this bug is not present there.
this bug is also not present in 0.9.3 for the -curses, -tty, -gnome3, or -qt4
pinentry's, so it's gtk-2 and 0.9.3 specific.
Also, if i paste a long passphrase into pinentry-gtk-2, it appears to work fine.