I see we can’t make it out of the first paragraph with a factual inaccuracy.
Benjamin T. Awesome

What if, say, 100 million people followed her advice?

If 100 million people considered voting for a third party, then 40 million would decide they actually liked the one of the two existing parties, another 30 million or so would decide they didn’t like any of the existing third party options, and the remaining 30 million would divide themselves between the various third parties on offer. The result would be that those last 30 million would have no voice in choosing the president this time.

In the following election, encouraged by that unprecedented third party support, more serious candidates might emerge (for instance, if it had been this time, Bernie Sanders might have run as an independent), and so if the same 100 million followed her advice for a second time, a third party candidate might win. Unless the vote was split too many ways; even in this second-time’s-a-charm utopia, plurality voting could still screw things up.

You know who is never in favor of changing the voting system in America? Democrats and Republicans.

Not true. The Democratic parties in California,Colorado, Maine, and Minnesota all express support for improved voting systems at the state and local level and the Democratic Party in Oregon considered doing so as well. In their convention rules, the Utah State Republicans also used improved systems.

Is there a majority of support for reform in either of the major national parties? Not yet. But if we’re going to get there, we need to be able to use both carrot and stick, and that means acknowledging the progress already made and the possibility for further progress.

It does nothing to contribute to some organization devoted to reforming elections if people championing that organization are also urging people to vote for candidates representing the major parties.

I should clarify. I speak for myself here. I am a board member of electology.org, but my fellow board members and the membership at large are extremely diverse politically. We include committed supporters of at least 4 American parties. How many organizations have Greens, Libertarians, Republicans, and Democrats working side-by-side for a common political goal? I regard many of these people as my friends, and I can assure you, they’d disagree with some of what I’m saying here, and yet we wholeheartedly agree on the goal of election reform. I think that you and I could probably see each other in this same way if we tried.