honestly, unless you are training in the same style then your rank should be honored. however, as an instructor, i always thought it was good to see where a student's skill level was at if they studied previous martial arts. i wouldn't let them wear their current rank, but, i let them wear no rank until i saw how they measure up. i've done it before. i had a student come to me as a brown belt in shotokan. there was no way i was going to start him at white because he had skill. however, i did start him at orange and caught him up with all the material he needed. he moved thru the ranks rapidly. if i went into a different dojo, even though i'm a 2nd degree black, i'd happily wear a white, and actually have done it. if i don't have a black belt in their style, then i don't deserve to wear that rank in their dojo.