misfeature

misfeature /mis-fee'chr/ or /mis'fee`chr/ n.  A feature
   that eventually causes lossage, possibly because it is not adequate
   for a new situation that has evolved.  Since it results from a
   deliberate and properly implemented feature, a misfeature is not a
   bug.  Nor is it a simple unforeseen side effect; the term implies
   that the feature in question was carefully planned, but its
   long-term consequences were not accurately or adequately predicted
   (which is quite different from not having thought ahead at all).  A
   misfeature can be a particularly stubborn problem to resolve,
   because fixing it usually involves a substantial philosophical
   change to the structure of the system involved.

   Many misfeatures (especially in user-interface design) arise
   because the designers/implementors mistake their personal tastes
   for laws of nature.  Often a former feature becomes a misfeature
   because trade-offs were made whose parameters subsequently change
   (possibly only in the judgment of the implementors).  "Well, yeah,
   it is kind of a misfeature that file names are limited to six
   characters, but the original implementors wanted to save directory
   space and we're stuck with it for now."