Old Reddit communities could look ridiculous.
That was partly the point.
Subreddit moderators could use custom CSS to change colors, layouts, headers, sidebars, labels and sometimes nearly the entire visual identity of a community. A subreddit could look nothing like the one next door.
When Reddit began preparing its major redesign, that freedom became a product problem.
CSS was powerful because it could break things
In 2017, Reddit told moderators it planned to deprecate CSS in the redesign and replace it with structured customization tools.
The company’s explanation was specific. CSS only affected the desktop web experience, was difficult to learn, could create confusing changes, and made Reddit’s own interface development harder because platform updates risked breaking custom styles.
Those are legitimate maintenance problems.
Arbitrary CSS gives community operators a lot of power precisely because the platform cannot completely predict what they will do with it.
Reddit’s replacement offered controlled options for community appearance that could work consistently across redesigned desktop and mobile interfaces.
https://redditinc.com/news/an-update-on-reddits-redesign
A theme editor is not the same thing as a stylesheet
The redesigned Reddit added options for banners, colors, icons, menus and widgets. That covers the common cases and is much easier for nontechnical moderators.
What it does not provide is arbitrary control over the page.
Old Reddit CSS could be clever, ugly, funny, inaccessible, brilliant or completely broken. It could also implement little interface tricks the official product never anticipated.
The structured system narrows that space. A community gets choices from the platform’s menu instead of control over the underlying presentation layer.
That gives Reddit a more predictable product across devices. It also makes communities look more like variations of Reddit rather than separately designed places that happen to live on Reddit.
Standardization has a real cost
A consistent interface is easier to support, easier to update and easier for new users to understand. It also gives the platform stronger control over where navigation, promoted material and new product features appear.
That does not prove advertising was the reason Reddit moved away from CSS. Reddit’s own stated reasons centered on mobile compatibility, complexity and development speed.
The loss is still measurable.
Users went from a system where skilled community operators could rewrite much of the visual experience to one where customization happens inside boundaries defined by Reddit.
The newer system is cleaner.
It is also less weird.
On the old web, those two qualities were often enemies.