Literally, diff is short for ‘difference’. As in, the difference between the two teams is X (eg. tank diff) and it means you’re blaming one role for being poorer than theirs…
So if someone says ‘Support diff’ they would be saying ‘their supports are better than ours’.
And yes its toxic. It spreads negativity.
I’ve never noticed anyone type or say X diff to be anything but toxic rude. They’re basically “rubbing salt in the wound” saying, “your X sucked”. Matchmaking put that person there which means you’re either the same equivalent skill level or matchmaking is broken so to say X diff is just rude and unnecessary whether true or not. It’s like someone T-bagging. It’s done to degrade and be toxic rude. I don’t think it’s worth it to report because Blizzard isn’t going to care about that but I’m not going to tell you not to. There’s not much you can really do against some toxic d baggery.
I’d like to point you toward a reply I made earlier in the thread. We have a way to fight it because Abusive Chat reports are sent to the automated system and once someone hits a threshold they will be punished regardless.
So - Please actually report things you find toxic in game. It might not be instant but reports add up. If it happens enough then those reports are stored on the back-end for 2 to 4 weeks.
If it’s quick play, sure report them. If it’s competitive, delusions need to be broken down. No, you’re not good at your hero if both teams say so. Accept this fact and move on to practicing before re-boosting your ego. Butthurt much?
Competitive doesn’t mean abusive behaviors gets a pass. Blizzard rules don’t have a “unless it’s competitive” exception added.
It’s not abusive, it’s competitive. No room for trying out new heroes in competitive games. You need to get grounded about your gameplay if you’re ruining other people’s competitive games.
Show me the rule that says it’s ok to be abusive towards other in competitive.
It’s almost never both teams that say so. I’ve yet to see a single situation where the differ was more than one guy who was pissed nobody babysat him
I have thick skin. I don’t care if someone says “diff” regarding me. I never say “diff” or put people down. HOWEVER. I will teabag occasionally, and I hope it doesn’t hurt feelings. I kind of enjoy it when someone bags me. It spices up the match, makes me want revenge. Hypocritical maybe, but it’s just fun.
gives me motivation, sometimes i feel like im just coasting through a game, but then i die and get tbagged, and a flip switches, my shots are landing more, i think through my attack lines, escape routes and target priorities. then when i get the kill on the enemy that tbagged me, i tbag them. and so it goes for the rest of the match.
tbagging is fun and shows sportsmanship
The level of narcississm in this forum/thread is amazing.
I come from a time that having thick skin is a way of life. Also, having accountability for ones action is considered maturity. Lastly, you stood up for what’s right and don’t back down.
If I’m not playing the game as well as someone else is, that is a skill gap and a [player] diff. Normally, i would say let it roll off your back and keep it moving. But i would also ask, “What can i do to be better?”. Calling a difference is the beginning of a conversation that needs to happen. Instead of legitimizing behaviors like so many of you have said.
If i see the tank in my group with bad positioning, im calling them out in coms, saying (Tank, come back! Cant heal you that far up!). Or if the other healer is outdamaging our damage dealers, i am saying something like, 'Come on, DPS. Don’t let (healer) show you up!". It’s making them aware without breaking them down.
People use the scoreboard stats to say “x diff” but that’s not the whole story, just some numbers that very vaguely reflect performance
I was playing Ana yesterday and got a healer, diff by my team and the other team, and it felt incredible. It was nice to be acknowledged for my efforts since endorsements are the most useless feature in the game.
You don’t want the BP levels, I SHOCK? 
That’s fine and dandy. We’re just saying it’s toxic to call out someone (who you perceive to be) struggling in front of the whole lobby.
When I was an NCO in the Army, I, like my senior NCOs and other leaders believed in: Praise in Public, Counsel in Private.
Any time you belittle someone in front of others, be it a LEGIT reason or constructive feedback, it affects morale. If you truly care enough to call them out, try actually helping that person get better at the game by reaching out and providing a solution.
I suspect that its easier to say, “There is not enough time at the end of a game to counsel them on their mistakes; so it is just easier to say x diff.”.
That’s a great motto
I think my motto is “Diff in public, teabag in private”
(not calling out the diff in public, just being better)
Someone messaged me after a particularly bad match and did just as you said. They told me I was the worst DPS ever, and I should stop playing the game.
They counseled me in private and provided a solution. 
Though I like your motto, sometimes a constructive comment mid-match can make all the difference. People don’t always see the mistake(s) they are making, and if you’re polite about it, they may just adjust.
The moment you start insulting team mates, they will intentionally throw or chat the rest of the match.
Only in 1 out of 100 cases does the criticized person pull their thumb out of their **** and constructively change their playing style.
So if you feel the urge to call out an obvious diff, do it at the defeat screen.