Mention macro is transformed into a block after the page is saved if inserted standalone on an empty line

STEPS TO REPRODUCE

1. Edit a page
2. On a new empty line, mention an user using '@'
3. Save the page
4. Edit the page again and try to type some text inline, after the macro

EXPECTED RESULTS

The Mention macro is displayed inline even after the page was saved and re-edited, so the text can be inserted right after the macro.

ACTUAL RESULTS

The macro is inserted in-line initially, but if no character is added after it, after the page is saved and re-edited is displayed as a block and has to be re-inserted to be able to insert text in-line after it.