Is it acceptable to paste shortened urls (e.g. those modified by tinyurl) in posts on stackexchange? I found No URL Shorteners?, which doesn't say no.
There are benefits of using tinyurl. One of them is making a post have less exposure because of not directly containing the original url, under the assumption that the owner of the original url doesn't prevent it from being linked either directly or indirectly via a shorten url. (Why would a post want less exposure? When a post asks about if someone's claim published on a website is correct, and some people don't take it well when they are challenged.)