Coauthorship across communities with differing standards One of the PhD students in my department is writing a paper and has listed me as a coauthor. I'm not sure if I deserve to be a coauthor.

I have been loosely involved in the project. I attended meetings and made suggestions and I actively proof-read the manuscript. But I don't think I had any significant input beyond that.

The student is in a different subfield and it seems their community has different standards for coauthorship. (The paper combines both subfields.) In my community, I would definitely not deserve to be a coauthor. However, the other community is less strict. In fact, there are other coauthors listed (more senior people) who, as far as I can tell, contributed even less than me.

I said something vague along the lines of "I don't know if I deserve to be a coauthor" and the student and their supervisor brushed it off. So it seems to me that, from their perspective, there is no issue.

I'm wondering what I should do. Surely others have experience with this sort of cross-community coauthorship. 

On one hand, I can just let them list me as a coauthor, as there does not appear to be any reason not to. On the other hand, if the situation were reversed, I as the lead author would not include so many coauthors.

Are there any potential downsides to being a coauthor? Do I have future obligations to reciprocate? Or am I overthinking this?
You say the work is done in their community, and two people in that community (including a professor) agree you meet their standards for authorship.

I see no reason to apply authorship criteria from your field to theirs.