It’s not specifically against any rules but any IMM I’ve ever heard comment on it claims that it makes them lose interest or go “bleh” on a character if they notice (and expect to be noted.)

That said, a sufficiently good role that you know went under the radar (little to no Role XP, no role contest entry, no Immteraction) may, being forewarned that it may get passed over for even existing, be worth the gamble if you’re creative enough to retool it and shoehorn it into a new character. Rewrite from scratch and have at it.