Omen, that would be silly, that would mean that even for channels that someone will only be in for a few hours for a support question or a file transfer or something would need to mark these clearly non-favourite channels as favourite =)
My suggestion was an "expected behaviour" feature, not really related to the status of a channel to a user (or to mirc); a reconnect with "keep channels open" and "rejoin channels upon reconnect" turned on does not need to pull the user into all the channels that he or she rejoins, preventing them from talking in a channel they were talking in when the reconnect occurs until all the channels have been rejoined.
the number of times I was typing something and suddently got pulled into several different channels while typing is high... you then need to backtrack through all the channels and remove the text that you inadvertently ended up typing fragmented over several channels, which is actually quite undesirable behaviour.
In this scenario the fact that all the switchbar buttons/treebar entries will light up should be enough of an indication that something just happened, leaving it up to the user to decide to check whether it's something that needs to be dealt with (which typically is not the case) or whether they don't care about that particular server/channelset at the moment because they're active somewhere else
