To quote part of KRyan's most-upvoted answer about the current policy (that was added in a later edit):
[...] we could allow system tags to be edited in without the OP’s input after a Meta discussion agrees that the situation is “safe” to edit. [...]
This is also my understanding after reading another of KRyan's answers to a recent Q&A of mine; that once a question has been taken to meta, and the community has concluded that a question is clearly D&D 5e (it's always D&D 5e questions that get the policy's attention), it's then OK to add the tag without OP's confirmation. The problem is guessing by yourself; deducing it within meta with community consensus is alright.
However, based on this recent meta question about a mainsite question that clearly 100% can only be D&D 5e, there are many upvotes and downvotes on many of the answers, implying that the community (at least, those who voted on those answers) is very split about this particular aspect of the policy.
So my question to the community is: is this part of the policy or isn't it? Is it OK to edit in the system tag without getting confirmation from the OP after it's gone through Meta and been agreed upon?
Just to be clear: this is not a question about whether this is a good idea or not, but clarification on whether this is part of the policy or not. Since we don't actually have a place where the exact details on the policy as it exists today are specified, I'm just trying to understand what the policy actually is, since there are conflicting opinions about it and no definitive source of answers.
(I think it should be part of the policy, but then, I'm against the policy anyway, at least the part about not adding it in when it's obvious, but clearly those against the policy have been overruled, hence why I'm putting this out to the community and keeping my opinion out of this).