If you go to https://gerrit.wikimedia.org/r/#/c/271740/ with Firefox and click on one of the user names listed under "Owner", "Reviewer", "Author", etc., the links point to https://gerrit.wikimedia.org/r/#/q/owner:dzahn%2540wikimedia.org+status:open,n,z et al. That page displays the overlay error message:
Code Review - Error
line 1:11 no viable alternative at character '%'
[Continue]
But in contrast to T127605, clicking on [Continue] will not display all open commits by the user, but an empty page (apart from the Gerrit header and footer).