Looks great overall, and the new Dark theme is a real eye-saver (Thank you!), but I did notice one thing I'm really not a fan of...
This feels like a massive downgrade in terms of formatting. Now there's no longer any way to make specific text bigger or smaller without it affecting the entire paragraph.
EDIT: Also might've found a bit of a bug; not sure if it's just a me thing, but the "Submit Reply" button doesn't refresh the page to display your reply if you're not on the last page of replies in the topic. This resulted in me posting this reply three times without me knowing (they all got merged into one, but I quickly edited my post to remove the duplicates).
Also, reputation numbers no longer seem to be accurate; my rep shows as 1.8K when I actually have 1,772. Maybe they should round down instead (if possible)?
Also also, though this may be a bit of a nitpick, but the Love reaction looks very similar to a Downvote from a distance.