We can only guess why users flag things, but in this case I'd guess it was because the submitted link (https://old.reddit.com/r/selfhosted/s/3CgRd01Ypw) just redirects to a login screen: https://old.reddit.com/r/selfhosted/login/?dest=https%3A%2F%....

Googling the title leads to https://old.reddit.com/r/selfhosted/comments/1bouuv7/warning..., which I guess is the same content? We can change the URL to that above.

Edit: oh, and I see several other commenters in the thread were already linking to that URL.