curious, why do you think separate irc networks is worthwhile?
if they are FOSS community then they should be all the same. of course, different channels, and different people, but all with the same shared ideals...
I think parent is worried about centralisation becoming a single point of failure. If IRC becomes entirely synonymous with Freenode, as soon as Freenode dies then the whole IRC dies as well. It’s a bit like Google Reader kinda killed mainstream RSS usage by centralizing it and then collapsing.
working on FOSS is the shared ideal. granted, this argument is aiming for the lowest denominator, but i believe that the idea that code should be FOSS licensed, for whatever reason, is already a good common ground.
moreover, those differences won't split along irc network lines. you choose the irc network based on where the project hangs out. for debian that would be oftc, which ironically was created because a number of people didn't like how freenode was run at the time. but anyone who was involved with debian had to move, regardless of where they stood on that issue or on their FOSS ideals in general.
if you work on multiple projects, you may be forced to be on multiple servers. no choice in the matter and different ideals have no influence here.