I have posted a comment on a question. The comment was deleted twice. The first time I thought I forgot to press enter, I re-posted it. In less than 10 minutes it was deleted again, clearly not because it was flagged. The comment was not rude, inappropriate or out of context. How can I find out who is the moderator who decided to remove my comment for no particularly good reason?
Conveniently, it looks like your comment was captured in chat. It was posted on this question, and read:
Not an answer, but you should not do it not just because it is a fraud, but also because marrying implies a series of consequences that may force you to have to support her financially for the rest of your life.
This is not asking for clarification or suggesting improvement, and that's all comments should generally be used for. Comments are definitely not for partially answering the question, or answering a question that the OP didn't ask. You may have seen more flexible policies on other StackExchange sites, but IPS is fairly strict, largely because the comment volume is incredibly high, and the answers are the goal of the site, not side discussions. It's a long read, but you can find further discussion of comment policies on this meta question.
So who deleted it? In this case it turns out it was a mod, but it could very really have been just a sufficient number of users via flags (no moderators involved) - it was noted in chat both times you posted it, and users in chat do exercise their flagging privileges. But that's not really the right question. You could've instead asked whether there was a good reason, and it appears that yes, there was.
I want to add that it is simply not true that just above mine there was a similar message that was not an answer. It seems strange that my message was deleted (twice) in 5 minutes, and others are not. It seems to me there is a lot of inconsistencies and I think this is a problem that should be addressed. The comment adds to the conversation, informs the OP of very strong and persistent consequences to his actions, similarly to the previous comments. It seems foolhardy for me to delete that, and only that one, comment.