As a follow up for T220145.
All cases refer to the page Wikipedia:Mentors on betalabs:
(1) If mentors add their user page link and that link has a display name - e.g. [[User:ET15|ET15]]- the description added after a pipe won't be displayed.
(2) If mentors add a pipe to their user link and nothing else after that, e.g.
* [[User:ET125]]| * [[User:ET15|ET15]]
Special:Homepage will be broken: the assigned mentor link won't be displayed (in the example it should be ET125) only wikitext of a following mentor's name: