The goal is to verify/ensure that using hash tags for campaigns parameters is allowed in Piwik.
Sometimes, it is a bit of a problem to link to example.org/?pk_campaign=test
Because search bots will follow these links, if posted on public places, and risk to index the URL with the parameter which will dilute SEO efforts.
Instead, the hashtag would make things better since it doesn't create a separate URL in the engine index.
See this forum post
(In ) Fixes #2475