First of all, I don't want to give a single yes/no answer for all questions about flavor pairing; I think it in general depends on how specific the question is. In practice, most (but not all) of them will probably merit closing, but a few well-written, specific ones won't.
Overly broad, open-ended questions should be closed. "What doesn't go with cheese?" is a good example for this, as is something like "what goes with chicken?" You can find examples of lots of questions like this we've closed by searching for "[flavor] closed:yes" on the main site, like questions about chocolate, potato soup, scallops, peas, and so on.
Obviously it's possible to ask much more specific questions about flavor pairing, though. If they're sufficiently specific, they might be too localized, but if you're asking something like "what additional flavors go with X and Y?" where X and Y are fairly different, so combining them restricts the list of possible pairings substantially, then you might have a good question. Some questions about traditional ingredients/pairings are likely also good. (I'm deliberately avoiding saying this is guaranteed to produce a good question.) For example, this question about carrot cake is great - it names a specific goal, and even asks about some specific potential ways to achieve that goal.
With respect to the specific question about oatmeal, I think it falls in the open-ended category. It's not as bad as "what goes with chicken?" but it's not great. While there's something general you can say (we tend to like "warm" spices with oatmeal, the kinds of things you put in spice cakes and apple pie), it has an awful lot of potential answers, and you can find plenty by searching for recipes for spiced oatmeal. The current three answers (including yours!) demonstrate this - there's some consensus between the answers, but given that someone even suggested orange blossom water, it's pretty clear that the list can go on and on.
The soup question is, I think, a red herring here. The actual question that ends up being answered there, and the reason it's helpful, is how to in general turn a bland soup into a good soup. The good answers talk about how to cook the soup, when to add certain things, emphasize the stock, and so on. The unhelpful answers are the ones that take the question at face value and just list some herbs and spices. If it were actually all about just spices, it'd obviously be in the open-ended (close the question) category, but it's turned into something better. I've edited the question to help all this out. It should definitely not be used as a precedent for open-ended flavor pairing questions, and protection via editing is nicer than literal protection.