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If you use any other account to post outside of meta then you will get banned for ban evading (if you are caught) - and will potentially get a worse ban.
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can you explain more about ban evading ?
So if my primary account got ban temporary,
I can't post using my second account ? or what ?
All I have really seen is a quote by theymos that says that he doesn't have a problem with people using multiple accounts as long as the purpose of the use of multiple accounts is not to evade a ban.
There seems to be precedent that people can post in meta while they are banned with their alternate accounts (they really should allow positing in meta if you are banned, along with the ability to PM administrators/mods so people will not need to create a 2nd account to discuss their ban).
I really do not have any additional information beyond the above as there does not appear to be any additional written rule.
I do not imagine that checking for and finding ban evaders is a high priority for the admins (although I may be wrong on this - I really don't know as none of my accounts have ever been banned to my knowledge - IMO they have not been banned period because I am knowledgable about the rules and follow the rules). If this is true then you probably would be able to get away with using a 2nd account as long as you are not caught, however the consequences for doing so will likely be more then the risk you are taking (I always advocate for following the rules).
My advice is that if any of your accounts are banned then you should not use any of your other accounts to post or PM, except in meta (to discuss your ban)