I think Active needs some harsher falloff for older posts. I always seem to see multiple days-old posts on the top under Active because they keep getting new comments which appears to bump them right back to the top. Recent comment activity shouldn't be weighted anywhere near as highly as the post being more recent, and I'd honestly prefer a fairly hard cutoff after 24~48 hours.
Wouldn't seem like it should be a problem but the end result of using Active is that every time I refresh I'm seeing mostly the same stuff I saw several hours or a couple of days ago. Hot always ends up giving me super recent posts (last 30~60 minutes mostly) where the comments haven't filled in much, while Active is leaning on too much older content. I find there's no happy medium like I had with Reddit where every ~4 hours I'd have a mostly fresh selection to look at.