I was asking for gold in trade chat (not a bannable offense as far as I know) and a minute later was disconnected and banned. This has never been a bannable offense, and I’m guessing I was mass reported by trolls in trade and auto-banned by the computer system.
How do I appeal this?
There’s no such thing as an “auto-ban”. The only way to receive a ban or suspension is if you were reported for breaking the rules and a GM applied a GM or if you get caught up in something like a ban-wave.
The e-mail you received would have given you a reason for thban/suspension.
You can appeal it via a ticket here:
https://us.battle.net/support/en/help/product/wow/197/588/solution
While you’re at it, you should probably request a name change.
Edited to provide same link as Vrak to avoid confusion 
Why would I request a name change?
The suspension, not a ban, had nothing to do with your chat. Asking for gold in public channels isn’t against policy, though it generally isn’t well received by most folks.
To be clear, there is no mass report = ban system, you were reported, certainly, but that generated a review of your name, which was found to be inappropriate.
You are welcome to appeal by submitting an appeal ticket, though I would recommend selecting a new name upon next log in.
I believe they are giving you a bit of common courtesy advice. I think eventually it will be adjusted, removed, or flagged for change regardless. Not really sure what initiates it (WOW or people reporting it as offensive), however my son had created a name for a character that was fairly inappropriate and it somehow was still allowed for a short time. About a week later he was required to change it. So he was upset about that, as well as the week ban I gave him for doing it in the first place when I found out about it! 
It already was as per the Blue post.
In the case of the OP, his name is what got him suspended, which means it was not a first offense.
Most of the time names get changed when other players report them. Blizzard does not go around policing names as a general rule. In this case, the player was probably reported for spamming/chat violations. As Vrak said, during that investigation the name was determined to be in violation which is what got them a name change and suspension.
Ok got ya, thanks for the heads up. After reading through I can see it woven in the middle there. I was almost wondering if that was the case, except my son wasn’t suspended. Likely as you stated first time offense leniency or something? Well he did get banned for a week from his local GM 
Yes, unless it is something SUPER terrible. If the person accepts the re-name flag and changes it to something acceptable, Blizzard does not do anything more to them. They will suspend only when the person re-makes the same name, or has a pattern of making poor naming decisions.
Solid parenting 
I always tell them to treat public chat/groups in game the same way you would a mixed group gathering IRL. If you would not say/do something around elders and small kids, don’t do it in game. A timeout tends to get their attention on that!
Yea gotta love the name changing that some people have to do…i recall a player on my server was reported for name… was something like RedBlue was auto logged and fopreced to change…he logged back in and was now named BlueRed…He didnt even make a minute in game before he got forced offline again. Then he logged on with a alt account and was whining in trade chat about the temp ban he got…was funny
No that was not the name he had but i honestly dont recall what it was now…just that he flipped the 2 words and tried to play it off*
It has been theorized, though I have never seen a definitive response, that if a player is forced offline for a name change, the GM will often watch the account for a minute while they finish up on the backend. That way they can take immediate action if something like that happens, or what I believe to be more common, they use the same name in a different variation
I don’t know if you’d say that we will specifically watch for it, but if they happen to log back in while we are finishing up writing up notes, etc… we may see what they decided to go with.
Is that how I got a three day suspension for immediately logging back in on a character I was forced to change the name of but renamed the same thing? Ive since renamed the toon something else but I dont play him, I just exercised some poor judgement due to boredom.
On a more serious note, that name is still possible to be created for some reason; it’s quite strange the name filter lets it through.
Probably because your name has a blatant shorthand reference to a certain body part on one’s upper body…?
Also just your usual reminder in these kinds of threads that names are changed due to being inappropriate, not necessarily “offensive”. They are different things. Nobody’s made the confusion yet, but figured I’d throw it in here anyways.