Just drop the offending image onto the icon in the dock.
Also, I just checked and Powerpoint has no problem dropping in a webp image. Gimp opens it just fine. You are right that web forums are often well behind the times on this.
If he's using ⌘⇧4 to take a screenshot, he probably isn't going to open it in Microsoft Paint.
I once edited Firefox config to make it pretend to not support WebP, and the only site that broke was YouTube.
bin/webp2png:
#!/bin/bash
dwebp "$1" -o "${1%%.webp}".pngWindows didn't use to show .jpgs in the window explorer. I know becase I wrote a tool to generate thumbnail HTML pages to include on archive CDs of photos.
To solve this problem, some format has to "win" and get adopted everywhere. That format could be webp, but it will take 3-10 years before everything supports it. It's not just the OS showing it in it's file viewer. It's it's preview app supporting it. It's every web site that lets you upload an image (gmail/gmaps/gchat/facebook/discord/messenger/slack/your bank/apartment-rental-companies, etc..etc..etc..) I just takes forever to get everyone to upgrade.
WebP gets pushed into your series of tubes without your consent, and the browser that you're most likely to use to view them just happens to be made by the same company that invented the codec. It's DivX and Real Media all over again.
Cmd+shift+4 is now the only way to grab an image out of a browser. Which is annoying.
It has made my life needlessly more complicated. I wish it would go away.
Maybe if browsers auto converted when you dragged ann image out of the browser window I wouldn’t care, but when I see webp… I hate.