Safe to change permissions/ACLs for `~/.ssh/known_hosts`? My initial problem: I am using git with SSH for authentication. Each time I push/pull, I get The authenticity of the host […] can’t be established, and after confirming to trust the host, I can connect successfully, but the confirmation is not recorded: Failed to add the host to the list of known hosts (/Users/peterlefanulumsdaine/.ssh/known_hosts).

The cause appears to be restrictive permissions/access control lists (ACLs) of the file ~/.ssh/known_hosts, as described e.g. here.

peterlefanulumsdaine$ ls -le ~/.ssh/
[…]
-rw-r--r--@ 1 peterlefanulumsdaine  staff  6795 18 Feb  2015 known_hosts
0: group:everyone deny write,delete,append,writeattr,writeextattr,chown


and the obvious solution, as suggested at that link, is to clear the ACLs with sudo chmod -N ~/.ssh/known_hosts.

However, I am wary of changing permissions without knowing something about the reasons for the existing settings.  So: why are the default permissions/ACLs for ~/.ssh/known_hosts restrictive, and is it safe to make them less restrictive by clearing the ACLs?

(I am on Yosemite, 10.10.5.  I haven’t ever tinkered with ~/.ssh/known_hosts by hand.  The only tools I directly use that I would guess might have affected it are ssh, git, and brew.)
It's perfectly safe. The unix permissions you have set there are enough. I don't have an ACL on my known_hosts file.