Thread:Big the cat 10/@comment-30701659-20190116162621/@comment-27150398-20190117192218

12. No Death Battle's of alternate forms of a character, with the exception of alternate timelines or worlds (Link Battle Royale).
 * As of March 25th 2018, alternate forms that are entirely separate to the main version of a particular character (ex. Archie Sonic, Paper Mario or Anakin Skywalker) are allowed, along with forms that can’t normally be accessed by said character (ex. Sonic the Werehog or Gogeta). However brief forms that are a normal part of a characters arsenal such as Super Sonic or Super Sayian Goku are still not allowed to solely be used due to the lack of feats they have on their own.

That’s exactly what I’m saying. As the alternate form rule states forms or transformations that can’t normally be accessed by a character ARE allowed to be used (such as Dark Sonic for reasons you already pointed out) whilst transformations that are a normal part of a character’s arsenal (such as Super Sonic) aren’t allowed to be used on their own. I realise that this might be a bit confusing to understand since whether or the rule applies depends on the specific nature of the transformation/alternate form but said rule DOESN’T apply with Dark Sonic and so that’s why he is allowed to be used.