When I first started reading Tumblr blogs I was confused about the themes people used. Depending on the layout, the far side of quote pyramids often becomes so ridiculously narrow that all characters are stacked on top of each other. Conversations become unreadable.
Some other, modern themes use a different layout that doesn't have that problem.
I wondered why people put up with the old style until I found out that the usual way participants look at conversations is on their dashboard, which discards themes and uses the modern layout. People don't look at their own blogs. Blog themes aren't designed for reading. Only people without accounts have to deal with that, but they can't complain because they don't have accounts.
The whole reblogging system is a disaster. It's like a comment tree, but you can only look at one branch at a time.