Is there a rule against a single person playing multiple accounts? Or is it just bad form?

Only if these accounts play against each other in the same game (on different teams or in FFA) or are used to manipulate ladder ratings. Teaming up with yourself is fine.

https://www.warlight.net/wiki/Rules "You shall not operate more than one WarLight account in a way that gives you an advantage in a game, tournament or ladder."

https://www.warlight.net/TermsOfService "Only one Account is allowed per person for playing coin games. Multiple Accounts, as well as the setting up and operation of multiple Accounts, are prohibited if playing with coins."

Note that colluding between players is not against rules, but operating multiple accounts in one game makes colluding easier so it fall under "gives you an advantage".

So teaming up with alts in a coin game is not allowed.

Edited 9/8/2016 16:02:09