I generally don't use reinforcement thread. as when I get to the heels, unless the pattern says otherwise, I'll usually make the heel denser than the rest of the sock by doing a s1, K1 on the public side and s1 then purl back on the private side.
Wisdom is knowing what to do. Skill is how to do it. Virtue is getting it done.
That which does not kill you, isn't trying hard enough.