Using relative URIS in wikitext is technically invalid wikitext but the last modified bar code  relies on this with wikitext in the form:
e.g. [/wiki/Foo test] by [/wiki/User user]
This caused a recent regression T259565.
While I am sympathetic to our use case here - we should be able to do this using interwiki links
e.g. [[Special:History/Title|title]] edited by [[User:Jon|Jon]]
Note: the history page may have to be an absolute uri for wikis where Special:History does not exist (I don't think there's an easy way to link to action URIs?)