I was working with a client with a MOSS 2007 implementation where MySites were completely disabled and making heavy use of user profiles. Eventually, we noticed that when a user clicked on a hyperlink to get user information they would be redirected to http://MySiteHost/Person.aspx?account=something (we will refer to this as the Person Page or PP). The problem was that the client had not branded the MySites host and did not want users to navigate to it whatsoever. After some digging we found that the hyperlinks were actually linking the users to http://MySharePointHost/_layouts/userdisp.aspx?ID=### (we will refer to this as the User Info Page or UIP).
Some research showed that users navigating to UIP would automatically be redirected to the PP when the a user profile existed for the user being displayed in the UIP. After making sure MySites were in fact disabled in our production farm and reading a some posts on the TechNet forms we came across the answer. We needed to uninstall the MySite feature from the production farm in order to disable the redirection. This was easily accomplished by a simple STSADM command:
stsadm -o uninstallfeature -name MySite