Wow, glad you had fun exploring. It suddenly made me think of a little feature that I'm not sure we made the best job of exposing. In the little trophy icon toggle on the right, there's the Top Ten list of views, then under those there's a little line that just says "In current viewport: 123km". Did you see that? Did it make sense? I implemented it, so of course I know that it's better than clicking all the points around a peak to find the longest view from a mountain summit. But maybe it's not obvious to other users? What I do is zoom in so that the viewport only contains the area of the summit (or indeed entire country for that matter) that I'm interested in, then I look at that "In current viewport:" line without having to click anything.
So using that, I would say that the longest line of sight in North America is from Mount Rainier, at 390km, looking North West into Canada: https://map.alltheviews.world/longest/-121.76853942871094_46...
Oh, I missed that!
That gives a longest in NZ of 365.3 km from Ruapehu, skirting past close by Tapuae-o-Uenuku (in the Inland Kaikoura Range) to a point on the Seaward Kaikoura Range near the peak of Manakau. Clicking on the actual Manakau peak also gives 365.3 km back to Ruapehu.
I can't seem to find a peak to get a reverse path back to Mt Ranier. Everything I try gets stuck in the Olympic Peninsular. (I was there once ... 1998 or so ... a place called Hurricane Ridge IIRC)
Right, I think we need to make that "In current viewport" thing more prominent somehow.
So this is the NZ longest line right https://map.alltheviews.world/longest/173.61386108398438_-42...
One thing to note about finding reverse lines, is that they're not truly mathematically identical because the observer always has a height of 1.65m and the destination is always some point at the surface, therefore 0.0m. It doesn't always make a difference, but it sometimes can.