According to this sign in the Powell Street station, one of the 16 posted bicycle rules has been stricken from the record. Taking a companion bicycle on BART is now 1/16th less hassle, a savings of 6.25%!
After close scrutiny of the redacted rule, we thought we could make out the word "confiscated" - we are certainly not sorry to see that word disappear from BART's bicycle-rule vocabulary. That is, if it has indeed disappeared - it may be that BART used black highlighter to emphasize the former Rule #15.
A quick check of the BART Bicycle Rules website provides no definitive answer - the web page lists a lucky thirteen bullet points governing bicycle behavior, but who's counting? The word "confiscated" does not appear, but a bike parked in an inappropriate place may be euphemistically "removed."
N.B. Our calculations of 1/16th less hassle do not account for the final, seventeenth entry on the posted list: "Be sure to sign your bike permit." This reminder, underlined and printed in all caps, is not numbered, so we take it to be some sort of VERY EMPHATIC guideline, rather than a rule per se.