I'm posting this just because I didn't think this could actually happen or was even a concern, and I think other people should know. I received a new baking sheet yesterday, and I had a hard time getting the adhesive from the label off of the sheet. So, I scrubbed at it with a little BKF, and as a result the area where the BKF was is now scratched up (it had a mirror finish before) and darkened in color.
I've always had BKF recommended for using on non-anodized aluminum, and I use it on SS all the time without problems, but I've never seen this happen before. (The only aluminum piece I've used BKF on before was already damaged because my partner put it in the dishwasher.)
I definitely won't use BKF on aluminum again, and I am going to contact the company too.