Usually this isn't a problem, because the comments are marked as
template-generated and we don't allow replying to them. But we had a
special case where we were trying to skip over some invisible
elements, which was causing us to skip into the middle of the
about-group in some cases. When Parsoid sees that, it serializes the
contents twice.
Bug: T290940
Change-Id: I9fe0b8d43ab874ccef371990799f77bfc46bc954