That's exactly what i would favor as well. Bans should be reserved for offences like repeat personal attacks and so on, it's too harsh for off topic remarks.
Best thing to do would be to cut the off topic posts from the update thread and move them to a separate one, opened by a moderator. Since moderators can't waste their time categorizing each off-topic discussion in its own thread but would lump everything in the same basket, we would be left with a thread that's hard to follow for our side-tracked musings. This would gradually force us to open up separate threads of our own whenever we wanted to go on a tangent.
Sad but true, causing a minor inconvenience to upset the modus operandi is the most effective means to make people drift to a different one