I also believe that displaying flags by default to users that have less than 7 days of logged in time is not enough.
Imo, the time limit should be raised or the display of existing flags should be made more obvious.
7 days log in time takes quite a while to acquire and I believe was adopted as the bear minimum for a user to have gotten acquainted with the trust system and how to protect themselves from scams. I understand that it targets, newbies, jr members, members and in some cases also full members.
I would not mind the flags being made more obvious on comments of the user. The '#' is not very conspicuous. And not all flags attract the "Warning: Trade with extreme caution" text.