Hello there. Earlier today, I noticed a few messages about a chat dispute elsewhere that mentioned chat logs and screenshots as proof. As Sannse noted, both are illegitimate as proof. A large amount of users, however, don't know that or don't know why. So I would like to take some time to explain that.
First of all, let me explain what a screenshot is. A screenshot is a picture taken by a person on a computer, game, or television, which captures the image of the screen at that moment. There are many, many programs for doing this, with the most popular of which [arguably] being PrtScr by LightShot. Most of these (LightShot especially) feature a host of editing tools. Most of these are useless for actually editing the contents of screenshots, but are rather useful for highlighting issues and other points of interest in a screenshot. That is, in a nutshell, a screenshot.
Next, I'll explain what Chat Logs are. A chat log is a (typically long) pasted bit of text that is copied from a chatroom and pasted into a document, usually via PasteBin. The document is then used as proof for the contents of a chat, typically for humor or to settle disputes. That's a chat log.
While I'm at it, I'll go ahead and explain chatlogger bots. These bots are ran by one or more users and feed the contents of a chatroom directly into a page or document--URL, by Sactage, is one such bot. Some of these aren't powered by web scripts, so they can be ran outside of the Wiki and paste their logs into a document on the host's computer, but this is still not infallible and should be trusted only when done by a trusted user.
Why can't these be proof, though?
Good question! Most of the time, what users do not realize is that both of these can be edited, very fiercely, in fact. If a screenshot is of, say, a web page, then Google Chrome's Inspect Element tool can be used to edit the contents before ever screenshotting--and since the changes are saved without any evidence of ever having used Inspect Element, no one can tell that it was edited. A user can, after editing, screenshot the web chat and post the screenshot somewhere and it may be accepted as legitimate. This can get innocent and even helpful users in trouble. That's why Staff and Wikia Admins as a whole should, and can not, accept screenshots. There's too big a chance they're made-up.
Chat Logs, on the other hand, are extremely easy to edit, especially after being pasted; most pasting sites don't have a tool that automatically formats it, so users must edit it to be properly formatted anyway. This means there is a high chance for any chat log to be edited. Chat Bots that log chat are extremely reliable and log chat without interference, but even they aren't the perfect solution--these logs can often be edited after the bot saves them. That's why Staff are reluctant to use even Chat Bot logs.
The main issue with screenshots and chat logs as evidence is that Staff cannot infallibly tell if someone is an experienced PhotoShop expert, or someone who barely knows how to use a computer. Thus, they cannot guarantee the honesty of the user or the integrity of the screenshot. It is very easy to claim to be a horribly inadequate Photoshop/inspect element user, even if you're actually a graphic designer or a very skilled computer user.
I did. Earlier today, I did an experiment. I wanted to know how easy it was to fool users into thinking something had been said totally different than what the message really was. So I took a screenshot before editing...
And then I edited it with Inspect Element. The second photo is below...
Both of those files look totally legitimate. Only the first one is. I edited the second one.
See why screenshots can't be used? They're not even slightly useful as proof, because they can be manipulated so much. Chat logs are the same way.
Check out this paste I made on PasteBin: http://pastebin.com/7CZAn2Dd
That one is legitimate and unedited. However... http://pastebin.com/Vde3RrHu
This one is not. It is edited and illegitimate. The second one is totally useless and wrong. But they both... Look... Legit. Only one is.
OK, so I have multiple users...
Note: after posting, I noticed a user said some things about multiple users telling the tale--users not directly involved with the issue. Something needs to be said on that matter.
If you have multiple users, unrelated and unbiased, providing the same screenshots/chat logs, it's usually pretty certain that they're legitimate. You should, of course, search for minutely changed details and make sure that you're not just being lied to by an experienced liar, but for the most part, that is a better method of ascertaining your legitimacy. Staff won't always know that all involved are separate and reliable, though, and so will still stay safe and rarely, if ever, accept screenshots--even from multiple users.
With all that being said, always report users acting up! But if you want them punished, you'll have to have them caught in the act. While I am not a Wikia Staff member or an Administrator of this Wikia, I do have experience with this kind of thing, and I hope this clears up the grey area with screenshots and chat logs.