If I see a rank 1 character below level ~10, I'd say that's perfectly legit.
10 or higher, it'll say either newb (or at least legit character whom I can look down on for being really lazy about really easy missions) or RMT to me. If I see them running around in a group with 5 other rank 1 characters, never mind any issues with obviously RMT naming patterns, then it says RMT to me.
For each rank up to 5, there's really a level at which there's no reasonable excuse not to have that rank. You might not look like RMT, but you'll at least look like someone who needs to do stuff other than level and make gil.
Rank 6 requires organizing a 50-cap nuisance for 5-1 so I can see that being a stumbling block (same for rank 3, but that 25-cap fight is *really* easy and you only need a few people, and some jobs can even solo it), and rank 7+ doesn't get you any direct benefits (aside from gil and flag), so I can see people not interested in story, stopping at 6.
