The Graduate Application portal suggests that the statement of purpose should be only 400-500 words. Is a longer statement of purpose accepted?

Yes, this is just a guideline from the graduate school not from the department. The application portal will accept documents with longer lengths.

Please write a statement of purpose that allows you to really showcase who you are and why you want to do a Ph.D. We are interested in your previous experiences (work, research, outreach, etc…) that have led you to apply to the Ph.D. program. We are interested in why UF is a great place for you to do that. We want to know what you hope to gain from doing your Ph.D. at UF. Usually, applicants are able to do this in about 2 pages.