if it's buggy and doesn't work in your editing program... then yes, it is a "sin"... because the gist of it is that DIVX/XVID are not made for editing, where as there are
plenty of other codecs that ARE made for editing.
DIVX and XVID are buggy, just because they work one day, it doesn't mean that they will work another day. Not to mention they can cause timing issues, particles, they are lossy, and have a whole buttload of other technical problems when it comes to editing with them.