Typical waivers are:
move comments are quite often in direct format (!,?,!? etc.) rather than in NAG format ($1 etc.)
variants are often reported as comments, and they would be not browsable by viewers
comments are often interlaced with the moves, without the required braces
comments are often not synthesized into NAGs ("white wins" instead of $18 etc.)
the STR (seven tag roster) is seldom used
blank lines are used quite freely
variants are in parenthesis, that can be round brackets, but also squared brackets etc.