I’ve noticed that there are serveral site where problems concerning gpgol may be reported (e.g. g10code with http://bugs.gnupg.org, gpg4win with bugtracker or one the newlists here).
I’d like to know which one is the most useful and effective.
TIA
CC
Good question 
The official one is at bugs.gnupg.org.
It is the best site to not have a bug report
forgotten.
However, it is not the best one from a
practical point of view because you can not
add information to a report once submitted.
The GnuPG development team might have
an answer how this situation can be improved.
I’ll ask on gnupg-devel.