I think that it is fine to talk about a chronic illness during an interview. maybe it helps illuminate how well you did despite a long ongoing problem. But upon acceptance I would count on the interviewer on being discreet and not talking about it in the hallway - unless of course you first broach the subject.

remember applications are competitive. grant funding in the past years has stayed the same where inflation and costs have only risen. this has lead to decreases in program, which then leads to a more competitive applicant pool. anything you do to "level" the field is a good thing. it is not underhanded. you obviously did well enough to graduate undergrad. THESE are the things they want to know in a personal statement.