On the one hand, I want to disclose the fact in order to comply with the no overt self-promotion policy.
On the other hand, just about anybody can claim that they're the developer of a game and say anything and get upvoted just because they worked on it; I don't honestly care as I have stuff to do, but you guys should be upvoting because what I say is true and not because I am a wonderful person, or so I claim.
What should I do?
One thing to consider - does admitting you are a dev or whatever for a particular game make the answer any better or any more correct?
Likely it doesn't. Likely the only thing that matters is the specific information that you are giving - if it is correct in and of itself, then it should be able to stand on its own as a good and thus community rewarded answer. If the only thing that convinces people of the correctness of the information is the name attached to it, then the answer is likely problematic, as there should be no need to be like "I am a dev wooo" in order to create good, factual, and likely testable/confirmable results of applying whatever answer is given to whatever game is being asked about.
So how do we solve this? Thank people very nicely for their time, but perhaps edit out the whole "look I did this thing whee I am a powerful person with title x" bits.
Admittedly, that does not take the self-promotion aspect into account.
So, let's look at the spirit of that, rather than the wording. Yeah, theoretically, according to a strict interpretation of the rule as worded, you need to tell us each and every time you post an answer/question related to something you have created. But, I hear you saying, doesn't that make your claim that we should just edit out "I am a dev yay" mentions?
It might, if we were taking this idea of self-promotion 100% literally 100% of the time.
Here's the thing, though.
I might very well have been involved on that project you are asking about, and thus, I might very well know the answer.
Take Stack Overflow for example. I know there are people there who have done things that are well known (I am not a programmer so I suck at examples), but they don't have to shout it from the hills.
As you said, things that are only answerable by devs are things we don't want, so the fact that they are devs shouldn't matter.
I don't think this needs to be addressed. Questions which only the developer can answer are off-topic. If you are here to answer the question anyone can answer, why is being a developer going to make that answer better?
If an answer contains that information, it is likely irrelevant to the actual answer and could be edited out.
I think that there are at least two separate issues here that have to be handled separately.
The first is the self-promotion disclosure policy. This actually doesn't really matter much for game developers because it is very rare that you can answer a question with a link to a game (since recommendation questions and most identification questions are off-topic). A more common case is mods. If I create a mod that solves 17 different problems in Minecraft, I might be able to answer 17 different questions with a link to that mod (plus some explanation text for each specific problem). In that case I should absolutely disclose as required in the policy that I was the one who created the mod.
The second is impersonation. This becomes a problem when someone claims that they are a developer and uses that claim to lend weight to an answer. This is unrelated to the self-promotion policy because the answer is not promoting the developer's product. The problem here is that the claim of being a developer is not verifiable, and unless it is verified, the weight it lends to the answer is unwarranted. Since they are claiming to be a particular person, the impersonation rules apply and we should try to determine whether the identity claim is accurate.
In addition, an answer is correct independent of whether or not the person giving the answer was involved with creating the game. This means that any claim in the answer of being a developer is irrelevant cruft and should be edited out. If the answer cannot be verified and only seems to be correct because the answerer is a dev, then the question is off-topic for depending on developer knowledge.
