Why are some orange, some bold etc., what is the algorithm?
Aarav, please add more context around a question like this. We don’t know what you’re looking at. Please give us a page/observation reference, etc.
Since you posted this in “Forum Feedback”, I’ll assume you’re looking at something on the Forum. Perhaps the replies & viewscolumns (since I don’t see units like h for hours or m for minutes in your screenshot, which would apply to the activity column)?
If so, from what I can find it’s a Discourse (the forum platform) UX/UI feature called “heat”
yup, that’s it!
Glad to help!
Although for future reference, gcwarbler was correct that more context and details are helpful.