Saw "OPFS" and immediately misread it as OSPF (open-shortest-path-first)

I see they are testing this on a Mac. I am curious what the test results look like if the users home directory or even the dot directories are tmpfs. On Linux .bash_login can repopulate dot directories from a archive directory think skeleton files and the dot directories can be ephemeral mounted as tmpfs. The person can have a command to commit their ephemeral directories back to the archive if they want to "keep their changes" so to speak. Or automate it on .bash_logout.

    du --max-depth 0 -h -c .cache .config .local
    767M    .cache
    278M    .config
    2.2M    .local
    1.1G    total

a bit off topic but on the topic of fingerprinting here, anyone knows how reddit fingerprinting works at a rough level?

I still have trouble understanding what information can be leaked this way. Apparently it allows to check whether a particular website was visited recently, but the article is vague in this regard. Can anybody ELI55 this?