Hadn't consciously realized how common this is
a couple thoughts come to mind based on very little
-6w7s can come off like they're putting on a 7 schtick, so can 7s but 7s can seem absolutely trapped in that schtick, probably super subjective but I worry more about the core 7s when I see a high-octane 7 thing going on, with 6s it can be somehow obvious that that's not the core problem (7's like...the actual alcoholic who can only almost find meaning in life at the strip club, 6 is like college kid who thinks binge drinking and hedonism is cool

-for an exaggerated vibe of my perception, not actual characterization of types)
-7s come off more metallic and slidy, like a 7 changes course so quickly, 6 has more like...breathing pauses where they're more serious and earnest (though think this also depends on MBTI and so forth)
-6s are reactive, think this comes through, at least the few 7 seeming 6s I know, react to political things in very 6ish way (...not that 7s can't be political, but there's this different vibe to me...I mean anyone who is actively campaigning about specific issue will come off in similar way but in terms of people casually Facebooking their political views for instance, have a 6w7 friend who will do a lot of for example "THIS article about catcalling is why I don't feel safe walking down the street" (not just the safety but the sort-of reference to own experience, now the experience is backed up by some sort of authority, obviously there's also a 'see my fear is rational' and even when 6s don't talk about themselves I think that's something that comes up a lot?) and just don't see this kind of thing from 7s, I'm sure there are some who talk about catcalling or whatever but not in the same way, struggling to explain and don't want to go really long with this but...you get me?
-With 6s think there's a worry that their logic is wrong, not with 7s, also think this comes through a lot of times, in different ways (a lot of 6s get defensive, even the 7ish ones, I notice a lot of 7s will drop arguments quickly if they get bored and 6s can do this too...but they'll definitely key in if they think someone seems like they're proving them wrong
-Not good hard-and-fast rule but I'd say very generally that 6s tend to perceive insults (the world hates me) -and might have myriad of reactions to that including thinking it's funny, trying to turn it around- and 7s tend to perceive compliments (the world loves me...but hurts me anyways)
-^both types can come off as victimized by the world but core 7 downplays it, more of a side thread, and imo 6 tends to feel it's more personal (and often spins humour out of it!)
Other posts on this thread were better but just my personal observations, could be wrong