The module uses moduleID and tabmoduleID.  The only place there would be any descrepency is statistics.  This is only because we have to plan it out a bit better.

Allow me to attempt to clear this up a bit.  There are different things here to consider.  We have one portal w/ a single forum, one forum with a single master portal but it is shown on several pages (via group), multiple forums in a single portal, one forum in multiple portals and other multiple portal use cases.  This means we have about 4 use cases to consider for everything. 

First, everyone needs to understand that anytime a single user is shared among portals, they are also going to be shared in the forum module.  If it is the same userid, it is definately the same user even if in seperate portals.  I think in most stastical places there has been attachment to moduleID.  This means that most stats will display proper accept the one held in the footer. (Because it hasn't been too much of a concern for me yet)

This also means that the exact same profile is used among multiple portals and that this needs to be investigated even further.