Council of Elrond

Is it valid to play a character at a non-haven site even if it would bring the number of characters at the site to above seven, so long as the player then splits the company (through movement declaration)?

Or is it not possible to even play a character in such circumstances?

There are no executive rules that would prevent a company from exceeding size of 7 outside haven.

If companies must join at non-haven site and resulting company would have a composition that violates rules, one of moving companies must return to its former site of origin. An action that would cause such violation is canceled*.

AFIK nothing similar for operations that would cause exceeding size of 7 outside haven.

*) and We Have Come to Kill as example is doubtful.