The example for "Friends don't let friends make heatmaps without maxing out outliers"[1] is so common. It's also very frequent in stats visualisations in videogames. If you play strategy or simulation games they often have visualisations to help the player understand what's going on/wrong, but for heatmaps because of the effect of outliers the heatmap gradient is often pretty useless. For example in the game oxygen not included, frequently if you do the temperature viz, everything just turns to either blue or some shade of pinky-red, because if you have a volcano or other heat source all the other colours seem cool. So you can't distinguish between a 1000C volcano and your slightly overheating 270C steam room for instance, they'll just be a pretty uniform shade of pinky red, and your overheating 60C base will be blue because it's pretty cold relative to them. Meaning that heatmap is pretty much useless for diagnosing a bunch of temperature problems.
[1] Can't remember the exact wording but that one it's like number 6 or 7.
If specific temperatures represent a meaningful problem, your colours should be standardised to show those temperatures, and not be automatically generated out of the whole spectrum of temperatures you currently have. In fact, having the meaning of colours change depending on temperature changes sounds like a pretty bad idea.
Wouldn't log-transforming the data be a suitable solution here? Unless monitoring the temperature of the volcano is outside interest, in which case excluding it or marking it as an outlier indeed would be apropriate.
Oh sure, there's lots of ways you can do it. I'm just saying that people making viz for games often do it in a way that isn't actually helpful, and that's an example.
A friend of mine has a literal heapmap, i.e. an infrared thermal camera, and that actually displays obvious outliers in striped red and white like digital camcorders show overexposed areas. It's really useful because it works both as an alert for hotspots, and also as a reminder to ignore them.
[1] Can't remember the exact wording but that one it's like number 6 or 7.