I said I'd make a post explaining how I go about this, but I've been busier this week than I'd anticipated so I'll have to apologise that never came about. I might elaborate on this further when I have time, but for the moment, here is a simple version of how I make decisions based on these posts. This can be a temporary guideline until Pokemaster offers some insight into this, but obviously I think this is fair enough:
If it is open-ended, a duplicate post or for MovesetBot, it is not allowed.
What is open ended? If someone makes a post like one of the ones Mike described in the post you quoted (where they've just posted a team or moveset and openly asked for advice), it is not allowed because there is no focus there. Advice could be anything -- it could be changing one move or replacing an entire team, and none of it is inherently any less valid as an answer, if there are few to no guidelines at all as to what is valid. This is why those posts are not allowed, they are directionless and do not make it clear when the post is resolved. Hence they are "open-ended".
However, if someone has posted a team or moveset and asked with some specific guidelines, like "which move is better on this moveset?" or "which Pokemon satisfies [a, b, c] requirements for my team?" then we can allow it, because there is a clear point at which that post is resolved: when someone has explained which move is better or shown the Pokemon that best fits the criteria, to use those examples. We could allow questions like "is [x] move better than [y] move?" and "what Pokemon can do [a, b, c]?", so why can't we allow them in a team or moveset context too? If the asker doesn't ask for team advice and that's what people post as an answer, then we can take those people's answers down, because they didn't respond to the actual question. If people also ask for team advice trying to skirt the rule, then we can edit that out.
So long as the question has provided a basis for someone to make objective arguments to resolve a clear prompt, it is fine. This way, the question can be "resolved" and not answered endlessly -- this same principle same applies for every other question that we get here. The post you linked satisfies this guideline by including the team and the game, so you could potentially justify one Pokemon over the other if it fits the team better or is more helpful for the storyline. I don't like rules for the sake of rules, that isn't helpful to anybody. These posts harm nothing and don't contradict any of our other rules, so I don't see any problems with them.
Does this make sense? If you have any questions let me know, and I'll try to answer them when my classes are finished today.