it probably didn't have any effect on the hand.
This is a very slippery slope.
someone actively trying to lower your EV by giving information to your opponents
This is exactly the problem. In fact, by announcing that he will not raise, he is sacrificing his own ev to the benefit of all other players still holding cards.
Eh, I mean, it's kind of making a mountain out of a molehill, imho. While it's definitely not proper for players to talk about hands while they are ongoing, or try to instill action one way or the other, particularly in a hand that they're not even involved in, this shit happens. It happens live all the time too.
There's no dealers to police table chat or players' behavior in-game at SWC, so might as well chalk it up as an occupational hazard of playing online poker and move on. You know, like losing a pot because your internet or power went out.
Fact is SWC has been mute (or dead) for months now, particularly here, and other forms of social media. They've already stated they're not doing any more work on the current client and that they're happy to continue the majority of operations as is, regardless of most players' feedback/input. Embrace and accept that fact, or find somewhere better to patronize. I recommend the latter.
Also, as an aside, that's not how EV works.
If this is a tournament where stack sizes much shorter, it's a much bigger deal.
Except tournaments on SWC, last time I checked, averaged payouts comparable to maybe an hour or two of flipping burgers. And I'm talking net, not gross.

-BttB
You are correct that people will try to cheat you in all forms of poker. You are incorrect that the best way to handle this is to just "let it happen".