I think something harsher than 15min would be needed to really get the point across, 1 day seems reasonable. A warning message to this extent when people join and start d/ling would probabably even out the negative effect.
As has been mentioned, the bot does auto spoofcheck, it only asks for manual when this fails. If the bot didn't auto spoofcheck, EVEYRONE would have to spoofcheck. I also am fairmly of the stance that language has no place in being blamed for people not spoofchecking, no matter what language you speak, when people are constantly saying your name and repeating what to type, you should understand what is going on, unless you're not paying attention, or mentally handicapped. Both of these conditions affect most of the dota population, so this is the main reason we have so many losers who just sit around stunned when asked to sc, over and over.
Perhaps it would be nice to have an auto pubbing system or command available... but as for reasoning, 'to go browse interwebs' is not a good reason for this feature, it's an excellent reason against it. Ek0's response of it causing flood once again confuses me, I cant see any potential way this could cause flood if it's programmed even remotely competently. A simple !autopub on/off/toggle command that auto !pub's every say 30 sec seems perfectly reasonable (obviously disabling use of !pub while enabled). All this said, I don't personally think this feature is really needed, or does it take priority over some of the more immediate issues with the bot, but it would be something easy enough to add, and some would find it useful.