It does the same as the @ operator, except that it takes care to prevent a
very bad bug that existed before PHP 7. Details at
https://phabricator.wikimedia.org/T253461
If there are other issues or benefits, please write them on the task. The
overhead of AtEase is prerty minor, so really any benefit at all is likely
to tip the balance toward keeping it. But, in the event that there isn't
any, then perhaps we should slowly phase it out.
Best,
-- Timo