Hi Stewart,

As I understand it the subjunctive mood is used to express: Wish, Emotion, Doubt, Desire, Interrogative, Negation or a general statement.

So if one wants to express any of those feelings above then this would trigger the subjunctive mood to be used.

So when one questions or comments  "How come I'm not in the football team" to take your example, the point is -- does this question / comment invoke an emotion or wish or desire etc ? 

Hope you find this input useful.

Alan (Jim)

There are still 2 clauses with 2 different subjects - the translation of the question into English as "how come" hides the first clause subject which is the impersonal pronoun - ça or il. If you think of the first clause expanded  "How is it that " or "How did it happen/come to be that" it is easier to see. The question being asked conveys the same lack of understanding/doubt etc of the situation whether you or someone/something else is the subject of the second clause. Subjunctive required. See this link https://www.lawlessfrench.com/subjunctivisor/il-se-fait/

Just to underline why the subjunctive mood is needed in this case:

It is a question which arises from some kind of doubt, regardless of whether you ask it about someone else or yourself. Hence the subjunctive.

My understanding has always been that the subjunctive always applies after certain triggers, but when you're self-referencing you can get around it because the verb is typically not conjugated. So for example, the usual translation for "I need to go to the market" would be "J'ai besoin d'aller au marché". If you were to conjugate it would be "J'ai besoin que j'aille au marché". It's just that the latter isn't commonly used--but if you were to say it that way you would still follow the subjunctive rule.