I have seen many websites supporting multiple forms of the same URL. For example consider www.example.com/question1/ OR www.example.com/Question1/ OR www.example.com/QUESTION1/ etc. all lead to one page with say
<link rel="canonical" href="http://www.example.com/question1/" >
or a 301 redirect to www.example.com/question1/.
Does this affect the page rank anyhow or its just for seemless user experience or there is some other reason behind this?
Infact even stackoverflow/stackexchange does this. No matter what the text after the id of the question in url they redirect you to the correct question!