When using Moodle networking, some serious inconsistencies pops up when using forums.
Suppose a User (Called U) holding an account on Moodle A who is able to roam to Moodle B.
User U on Moodle A is suscribed to a course in Moodle B
Now a teacher in Moodle B posts a message in a forum in the course where User U is enrolled.
User U receives the mesasge in his email and try to reply using the message's "Reply" link
Clicking on the Reply link, User U is directed to the Moodle B login page, where he cannot login: he can login only in Moodle A.
User U can login on Moodle B only he is first logged in on Moodle A. This way, the links present in the forum body messages to participate to forums (and I suspect other activities) are completely misleading (and frustrating) for User U.
allow login of User U also in Moodle B, trough Moodle networking