The Jargon File (version 4.4.7, 29 Dec 2003):

miswart
 /mis?wort/, n.

    [from wart by analogy with misbug] A feature that superficially
    appears to be a wart but has been determined to be the Right Thing. For
    example, in some versions of the EMACS text editor, the ?transpose
    characters? command exchanges the character under the cursor with the one
    before it on the screen, except when the cursor is at the end of a line, in
    which case the two characters before the cursor are exchanged. While this
    behavior is perhaps surprising, and certainly inconsistent, it has been
    found through extensive experimentation to be what most users want. This
    feature is a miswart.


The Free On-line Dictionary of Computing (30 December 2018):

miswart

   /mis-wort/ [By analogy with misbug] A feature that
   superficially appears to be a wart but has been determined
   to be the Right Thing.  For example, in some versions of the
   Emacs text editor, the "transpose characters" command
   exchanges the character under the cursor with the one before
   it on the screen, *except* when the cursor is at the end of a
   line, in which case the two characters before the cursor are
   exchanged.  While this behaviour is perhaps surprising, and
   certainly inconsistent, it has been found through extensive
   experimentation to be what most users want.  This feature is a
   miswart.

   [Jargon File]