Does getting a double major in a humanities subject matter at all?

If you haven't networked enough to get a first round interview, a double major - even if its in STEM - will not make the difference in getting you an interview. If you have networked, a double major does not matter anyway. In short, it doesn't matter at all. You should double major in something if you are interested in it, or if you need a way to delay graduation to recruit again next year.

A humanities double major is an interesting talking point, and makes me think you likely have strong writing/communication skills... that said, it wouldn't make me pull the resume from the stack for one with solely a business major. Not something that moves the needle much.

I'd recommend a minor and spend the extra time on leadership activities. Those have a lot of impact for SA interviews.

I don't think it matters much, but it also won't hurt. You'll never get a chance to get a degree so cheaply again as undergrad, so why not do it? Esp if interested in both subjects.

Short answer: No.

But not everything in life needs to be geared toward getting a banking job. If you want to do it and it won't negatively impact your ability to network, get a high gpa, have some fun, etc then I don't see why you wouldn't. Just don't do it solely for IB because no one will really care.

I double majored (two separate degrees, in two separate schools at my University) in economics and finance and had multiple interviewers say I wasted my time on the economics degree and should have focused on internships. So be ready to defend that degree in terms of opportunity costs.

Given the saturation of finance/economics/business majors in IB, it would help as a talking point to help you seem more interesting in a networking/behavioral interview setting. That being said, adding another major is a decent amount of work and that extra leg up should be seriously weighed against the additional time and potential effect on your GPA it's going to have. If you think it might raise your GPA with minimal to the moderate effort while continuing to gain relevant experience in the industry, there's nothing stopping you.

It might help to make that second major be in a different discipline altogether. Bio/chem would help for life science IBD/PE, and computer science for TMT.