Comments are enabled on a page inserting <comments /> tag, which inserts the comments section at this exact place.
I'd expect comments to always appear at the end of the page. However, adding any arbitrary wikitext after the <comments /> tag renders it after the comments section, which could make that text going unnoticed.
Is there a reason for adding the comments section in the middle of the page instead of at the end? Apparently, this is technically doable: The Cite extension adds <references/> automatically at the end if it's not present on the page.
Also, I think categories could appear before the comments, to be more reachable (I doubt people would expect to scroll past the comments section to reach the categories).