How would an optional, official parser be toxic?

[Maeka]

I don't think an official parser would cause that much damage at all. There's already player created parsers for PC users, they've been around since ARR, there's already numbers posted at the end of FLs and feast, and WoW has most people using parsers, and I could count the times someone has mentioned them in-game on one hand, let alone abused someone for it. And if you do get abused for it, there's still the report function, blacklist, and you can still leave the party.

And with an official self-only parser, people won't really know what other people's numbers are anyway.
Also improvements means passing dps checks, getting clears, and why else do people play games, other than self-satisfaction?

Yeah, but FFLogs is a third party website and they don't record casual stuff like Roulettes and such, because nobody cares. However, if you could parse people in-game without the website, then I bet people could, and would, use the parsing tool to be jerks in content where you don't need parses, IE, leveling roulette etc.