[Vegenoid]

I think the problem is that the mechanism to trigger mouse-hover is not clear on a touchscreen - there are several different ways that need to be remembered and tried, as evidenced by your comment.

[qingcharles]

I wonder if a solution on touch is a (?) icon next to the human date? Or is that too much clutter?

[Vegenoid]

I like ? icons that can be either hovered or clicked on to reveal a popup with additional info.

[sanderjd]

Yes, but I think the venn diagram of people who really want to see a timestamp and people who are willing and able try a few different things to find it is pretty close to being a circle.