How can I be sure I'm looking at a sockpuppet?
You can't ever be 100% sure. What you think is a sockpuppet could in fact be my good friend Nog Shine, who loves everything I write, copies my writing style, and uses my computer to vote and post stuff when I step away for coffee.
But in practice, there are patterns that are extremely unusual unless someone is using a second account. If it actually is a very enthusiastic friend, they should know better than to continue this behavior after being warned about it. Feel free to contact the SE team if you're unsure - we have a fair bit of experience in dealing with this sort of thing.
When should sockpuppets be considered a problem?
There are a handful of legitimate reasons to maintain multiple accounts. A good rule of thumb for identifying abusive socks is: if the second account allows you to do something on the site that your normal account would be prevented from doing, it is abuse. Examples of this include (but are not limited to):
- Voting on your own posts
- Answering your own questions with the other account(s)
- Casting multiple votes on others' posts
- Supporting your own arguments ("+1: shog is right, don't know why the rest of you don't realize this")
- Using bounties to circumvent the rep cap
- Circumventing suspensions, quality bans, or the rate limits on posting questions / answers / comments / etc.
How should moderators handle problematic sockpuppets once they've been identified?
This depends on the severity of the abuse and the discretion of the moderator handling it. For the typical first occurrence:
- Send a warning to the primary account, and either send another warning to the secondary account or simply delete it if the abuse is blatant.
For subsequent occurrences (and first occurrences when the abuse is blatant):
- Suspend the primary account, delete or suspend secondary accounts.
I was suspended for sockpuppetting and feel this is unfair; I didn't realize it wasn't allowed / it was an enthusiastic co-worker / I swear it was my evil twin, Nog Shine!
Take this opportunity to get to know how the community here works / talk to your co-workers / send your doppelganger back to the darkest timeline.
Then just make sure it doesn't happen again. Everyone makes mistakes, and we don't hold grudges here.
You mentioned valid uses for sockpuppets; what are they?
I've probably had a half dozen or so alternate accounts over the course of the site. They're useful sometimes: testing bugs that only show up at low rep levels, reminding yourself what the site "feels like" for someone with only the basic abilities, maintaining a highly unnatural q/a ratio... That said, I always treat these as disposable accounts, and some of them have been removed (either automatically or via mod intervention) when I crossed a line somewhere - you should never assume that a sockpuppet is "protected" if you're actively using multiple accounts on one site; it's entirely too hard to be certain you're not interacting in some inappropriate fashion.