Proposed resolution:

In [istreambuf.iterator::op++], delete the three lines of code at the end of paragraph 3.

Following the definition of istreambuf_iterator<>::operator++(int) in paragraph 3, the standard contains three lines of garbage text left over from a previous edit.

istreambuf_iterator<charT,traits> tmp = *this;
sbuf_->sbumpc();
return(tmp);