This was quite useful in Bugzilla for cross-referencing similar bugs and I miss it often in Phabricator. One can just add it to the description, but that's much more effort.
This was discussed during the Bugzilla migration planning phase, and we decided not to migrate it. @Aklapper, do you recall where? Searching for "See also" today is not easy...
Editing the description does a click more than Bugzilla's open fields, and perhaps you want to add the URL with a sentence for context (which might be useful in itself), but I would not call that "much more effort".
Proposing to Decline this task.
PS: or are you proposing this as a request for Phabricator upstream?
"See also" today is not easy...
The intention was to simplify the UI a bit as Bugzilla had a horrible number of fields...
I really still like to know how often and in which situations people search for a known value listed under "See Also"... But let's continue in T76101.
Dropping "See Also" in the description field was once listed in the desc of T259 but without any further background explanation either. I'm a bit surprised that some people care, to be honest, but I'm still after specific examples of usecases.