Yes, such a feature would be '' misused '' by the worst people in the worst way. But the worst people are the worst people already whether parsing exists or not. The real dilemma and issue to me is if FFXIV creates their own in-game parsing logs that are as or if not more insightful than fflogs, what kind of culture does it encourage on all of the players, and what kind of effect that culture has on new players that are new to MMORPGs and online gaming in general, as well as casual players.
I do not think parsing would have such a huge effect on the already pervasive culture of optimizing even the most casual content, but any kind of feature that will allow better optimization across all content (and even encourages it) should be looked at critically before implementing it. A lot of people seem to just want to shove things into the game without looking at both sides or partaking in a more nuanced conversation about different levels of play (NOT calling out anyone in specific), and how the implementation of different features that encourage people to play more optimally will affect said players and their enjoyment.
If this was a purely competitive PvP game like a MOBA or Arena shooter, I'd say '' who cares about normies, casuals and low tier players, just balance the game according to the highest levels of play, most of the time anyway '' but this game is not that, and a parsing tool would mostly be there for people who raid extremes, savages and ultimates, so a minority of the players (in western servers at least).
But like I said, I don't think an in-game parsing tool would affect my or anyone else's casual play that much, but it's a conversation worth having whether it would or wouldn't.
