I can't trust a project just because a legendary members post their announcements thread, he can be paid to do so and i don't think forum rank really justifies the guenuity and legitness of a person.
You are right. Legendary rank won't guarantee that the project announcement is legit or trustable. Yep, the project team can pay him to make the announcement. Also, the level of ranks in this forum has nothing to do with the quality of a project announcement.