Take any of this post with a fair grain of salt. It's much speculation here.

Just repeating what already been said multiple times. Increased popularity in PvP is not due to chat restrictions in feast. At best it has little to do with it (did really feast participation grow THAT much after restrictions in place?). It's mostly due to exp, lvl30 entry and garo event.

What I'm guessing (again, this may not be true at all) is that SE are afraid of the toxic behavior in chat and what consequences that entails (multiple harassment reports etc.).

Of course there will be toxicity in a PvP environment. Most of it however, is, I assume, spur-of-the-moment, short tempered rage. No sane person lets a bad match ruin their life. But there will always be those few who can't let stuff go and constantly rages for every minor thing. Don't let the rest suffer on behalf of those people.

One could argue that people already having experienced toxicity in chat are discouraged to continue. I agree that is a fair point. But that's why you have the possibility to report people. Why SE did not chose this route is the reason for me guessing they simply don't want to deal with potential chat harassment (from a businesses perspective). Losing customers due to harassment does not make you look good (doesn't matter if it really was harassment or not). They are willing to sacrifice any potential losses from the tiny, pre-garo PvP community on behalf of all this.

Concerning cheating in feast etc.: I'm guessing, from a business perspective, they want to be 110% sure to punish to right people. If there is even the slightly possibility of legal play, they won't risk the bad-rep of potentially punishing innocent people. If this is true, I'd say it's enough to be reasonable sure because you can never really be 110% sure (maybe we live in the matrix etc.). But from a business perspective, they wont risk it.

Again, none of this have to be true. I'm just trying figure out why it is how it is. And I'm not saying Yoshida is lying (it's rather truths with some twists).