For example, currently all submission links on Benq's submissions page are grayed out (at least for a logged-out user); while this submission for example can be viewed normally.

This is a server-side issue. On that page there's this snippet of JavaScript code:

            var viewableSubmissionIds = [
            ];

The bug is not present on the second page -- there are both viewable submissions and unviewable submissions, and they are displayed correctly. I suspect that the bug is related to the fact that some of the submissions are in a running contest.

Of course, the viewable submissions are still accessible using the direct link.

Screenshots:

On the second page, the viewable and unviewable submissions are displayed correctly.

On the first page, all links are grayed out.

I can find this similar (8-year-old) blog, in which MikeMirzayanov said that it will be fixed, but the bug remains.