Fragment identifiers are traditionally used to identify a portion of document for client-side applications. As stated in the specification Google adopted:
Traditionally, hash fragments (that is, everything after # in the URL)
have been used to indicate one portion of a static HTML document.
...hash fragments are not part of HTTP requests (and as a result they
are not sent to the server)
Consequently as this covers, the Googlebot ignores hash fragments by default. Therefore for this URL:
Googlebot should just look at the resource returned by the server:
http://example.com/article/1543 while ignoring the hash fragment:
So essentially the resource for the above URL is the canonical URL after normalization (i.e., removing the fragment).
The purpose of using a slug is to identify a page as a human-readable keyword. Using a fragment confuses this purpose and obscures its readability:
/how-to-boost-seo is a lot more readable than:
So in short, using a fragment as a slug would not seem beneficial to users or search engines.