Depends on T64324: Visually indicate when a Phabricator user is new (Welcome culture) (being able to identify new Phabricator accounts).
For new Phabricator accounts, link to https://www.mediawiki.org/wiki/How_to_report_a_bug at the top of https://phabricator.wikimedia.org/maniphest/task/create/ - cf. T103556#1562205
There are enough papers out there about people not reading bug-reporting docs. Still it would not hurt for the small number which does, plus it seems to also depend on the wording of the message (there's a Zimmermann paper about that).
"Did you know that well-written bug reports with enough information get fixed faster by developers? How to write a good bug report."