The message is in its entirety accessible without logging in. I also see a lot of unflagged links to X on HN that show the login prompt beneath them, just like

The message is in its entirety accessible without logging in. I also see a lot of unflagged links to X on HN that show the login prompt beneath them, just like this one might show it, but it’s beneath the post on X. So I have to conclude that the reason for flagging my post might be a different one, but there is indeed a stipulations in the FAQ that you could base your flagging on. So you have the moral excuse to flag it, but don’t necessarily have the moral upper ground, because the post is entirely visible without logging in and there are cases of many unflagged links to X.