You know you played support well when...
you receive a friend invite from the enemy adc
you receive a friend invite from the enemy adc
Or because you're a Janna main and the ADC wants freelo
that happened to me once after I left post game lobby
...and the enemy adc proceeded to accuse me of hacking and scripting, then unfriended me.

Or when three of the enemy team are telling your ADC in the post game lobby that the only reason that they won was their support carried them. (Boy did I surprise an Ori mid by roaming as Zyra after first back and successfully killing her that particular game.)
You know you played Singed well when you get reported by the enemy ADC after winning a game.
I added a gift Thresh one time becuase we clicked and we both went aggro at the same time and played off each other and got fed and carried together and he called me a noob.
Granted he was plat, and I'm a lowely silver, but it was just norms bruh.
Feelsbadman.
Or when your adc does't flame you, Jk, your adc will flame you anyway.
#supportlife
Once enemy team agreed that I (Soraka) carry my team. Best moment ever :D
I got added by the enemy support a couple of times lol, never thought about it that way tho :P.
(bans janna as hates her low impact freelo)
You get mystery gifted other support champions.
I thought supports were always playing perfeclt and simply aren't allowed to be blamed for anything?
Well now I have a new goal next time I play.