Here we are looking at the short form of notifications,
Now I know what you’re saying. You’re saying “Dan, just push that mysterious down arrow that’s unnamed there on the bottom of the screen and then you’ll see all the details.”
Yes but show me one app no matter GitHub, Facebook, or even your cell phone itself, that doesn’t have the time, no matter how concise the notification list is!
I would say time is not a relevant data for a topic. And there isn’t actually space.
If that time would be visible I would bet there would be someone nagging how a small screen is way too crowded and discussion is not same as social media, where absolut no one is looking those tiny times that are no even is order.
I understand what you are saying, but why does the time matter? For a lot of notifications such as likes or badges, it’s kind of irrelevant to show a time. I know you’re on mobile but on desktop, if you view all your notifications, you can hover over the time for more precise information.
As Jakke said, Discourse isn’t the same as Facebook or other social media platforms it’s meant for asynchronous discussion. For example, when I open Meta I check my notifications and have a gander in my own time. I don’t suddenly drop everything (a bit of hyperbole here 
) after I’ve seen a notification from merefield replying to my post, thinking, omg, I have to reply now.
Perhaps your desired outcome could be achieved by a theme component?
Well, I suppose I could remember what that down arrow means and use it if I really want to see the time. Okay.
