[acqq]

I don't see favicons too, but I've just did one "image extraction" attempt:

https://news.ycombinator.com/item?id=12569999

700 KB of binary images in a 1.7 MB session file, which can be compressed only to the 70% of its size.

I also see a lot of things like \\u0440 which spends eight characters for one unicode character (in another file, not from me). But that file was reduced to 37% of initial size with LZ4. It seems LZ4 is still worth doing, if the content remains easily accessible with the external tools, e.g. lz4cli.