Is it appropriate to ask for donations on ones profile page? To me, it seems to be somewhat at odds with the goal of SO.
Yes. I believe it is.
There are very few places where you are allowed to advertise yourself or the product.
If people want to add donate buttons so people can donate them money if they helped them I think it's completely appropriate. It's not just that user, for example Gordon for example has an Amazon wishlist and that is appropriate as well.
- The issue of allowing payment for quicker answers was discussed and there is a consensus that it's a bad idea.
- You shouldn't ask for money on questions. Never, nor condition an answer on payment, or suggest it. That's not what this community is for.
Also, this is very similar to how it is allowed to promote your personal website, interests, favorite projects, tools and contracting & consulting services on your profile.