This isn’t true at all.
Many will say the same.
Still, both cohorts' language and behavior evince continuous cultural cross-pollination from around 2012 (at least; I wasn't paying serious attention much sooner), at a rate and scope both well in excess of broader culture's adoption of same as substantially attributable to either source.
That still has to be explained, and I would be curious how you do so, although you'll almost certainly prefer to keep trying to indict the factual claim.
Do you have any evidence or anecdotes to explain why you believe that?
> you'll almost certainly prefer to keep trying to indict the factual claim.
Because the claim isn’t convincing. I saw plenty of content from Tumblr in 2014 despite not actively using it, and I could probably pass an ideological Turing test for a user of the era, but that doesn’t mean I was using both websites. You obviously have to have someone taking screenshots of these posts for each community to be aware of the other in the first place, but the core demographic of users on each site did not substantially overlap.
As for the rest, I made a general factual claim that I'm happy to discuss, but I do not know you and neither can nor care to attempt to speak to your personal situation, so if you continue insisting on the latter I'll have to demur from further participation. I'm a student of and commentator upon the moment of history in which I happen to have found myself, rather than a social scientist or indeed any other kind, and also not your father confessor. If the result of my observation and analysis fails to satisfy your standard, that's okay by me.
Or we could try to have a conversation about it, I suppose. For example, what explains the trend of both cultures' slang growing more similar over time? Merely circulating receipts to make fun of doesn't seem likely to have this result; why socially adopt language unique to a common object of social-bonding contempt? And so forth.
I obviously don't have a lot of data for or against, and I think neither does anyone else for events too recent to have more than begun to be studied. I am one unemployed software engineer. You are free to demand I exceed in result the entire professional vocation whose job is this kind of analysis, but I can of course do nothing in response save disappoint.
