The post that was quoted here has been removedMost likely because they want cleaner spaceless "slugs" to match the account name? (And removing capitals because URLs are case sensitive too.)
Re Slugs from Grok :
In web development, a slug refers to a part of a URL that is designed to be human-readable and SEO-friendly. Here's a breakdown of what slugs are and why they're used:
Definition: A slug is usually the last part of the URL which describes the content of the page in a concise and clear manner. For example, in the URL https://example.com/blog/what-is-slug-web-dev, what-is-slug-web-dev is the slug.
Purpose:
SEO: Slugs help with Search Engine Optimization by including keywords that can improve the page's visibility in search engine results.
Readability: They make URLs easier to read and understand for both users and site owners.
Link Sharing: More descriptive URLs are easier to remember and share.
@You-As-Whole saidIt isn't.
Is it really that much harder to allow uppercase and spaces?
edit : Although I can think of a minor performance benefit, they would not need to convert from account name to slug and back again when working with account names, so just one account name is stored, which is a suitable slug with no further work required.