The rest of the answers have dealt with the main issue here. I'd just like to explain why IP address banning should never be used on Stack Overflow.
IP address bans are a Very Bad Thing
They raise these questions:
- What if he's using a cyber cafe?
- What if he's part of a shared-IP address network? Many workplaces have these where the external IP address is the same (this is called something, but I don't know)
- What if he's at a friends place?
- What if his IP address is dynamic? A WHOIS can tell you this, though.
- What if he's using a proxy? A WHOIS usually tells you this as well, otherwise there are lists of proxies available
They're easy to bypass:
- Switch to a different computer
- If you use a dynamic IP address, renew it.
- Use a proxy. And no, this doesn't mean we should rangeblock all proxies like Wikipedia does.
The other issue is, we need a way to appeal against these. And that means another system.
You mentioned Wikipedia. Well, you're right, Wikipedia employs IP address blocks extensively. But, there are a lot of mechanisms required to appeal against blocks. There are a lot of "collateral damage" cases, where too many others are affected by the blocks. I used to help out at their Account request system (this deals with people who cannot create accounts, due to blocks, rangeblocks, accessibility issues and whatnot). And a lot of its requests are due to the collateral damage of blocks (it surprisingly gets a sizable number of requests per day). There's a separate mailing list monitored by a whole bunch of people for editing-blocks as well. And, blocks can be appealed on the IP address talk page itself (though these appeals are usually a bunch of drama).
Anyway, if we started IP address banning, we'd need a similar system in place to appeal them. I guess emailing [email protected] would work, but that really doesn't cut it when you want to tell apart "someone who's been wrongly affected" and "someone who's been collateral-damaged".
Basically an IP address ban is a whole lot of work for the banner, when it is easily bypassed by the.. uh.. bannee.
So, I say that IP address bans should be reserved for extremely special cases, where they are absolutely necessary. This is not a special case, this is just a troll talking big.