silverbacknet
So many websites I remember came back up with "the last two weeks of posts are gone, sorry" or just shut down for good because it was all too corrupted to fix, and so were the backups, if they had any.
If it's true, it's an interesting peek into his mind, and confirmation of some public vs private social mores, but all the pontification on society and morality and futility is just so much old man yelling at clouds.
The PNG and GIF comparisons are unfair; they're the same low resolution as FLIF, but given nearest-neighbor upsampling instead of bilinear. Most web browsers use bilinear or bicubic upsampling for progressive pictures now, so FLIF isn't nearly as unique as it presents itself. Aside from that, progressive is only useful if you're on a slow connection or the file is broken; in other cases re-rendering multiple times becomes a bottleneck and battery drain. In general it's rare that progressive decoding is a win anymore (although progressive encoding of JPEG is always a win).
In another comment I pointed out that jpeg2000 can be encoded to any size, even 1k, even though the q-scale doesn't go that low, by using the target size parameter instead. It looks better than anything but BPG and is fully progressive. Of course, J2K is a dead format outside of DejaVu, PDF, and the medical field, but it serves as a useful baseline.
A comparison to JXR would have been nice; it's an open, patent-indemnified format that fully supports progressive decoding, and compresses about as well as WebP. That format's the biggest disappointment for me, I thought it had everything in place to displace JPEG.
BPG could be made somewhat progressive, but only by changing the underlying HEVC bitstream, while one of its goals is to stay as close as possible. The inclusion of a thumbnail is the only recourse.
Looks better than anything else but BPG at that size, to me, although FLIF obviously isn't optimized for lossy.