I agree on this. I'm a new user and I'm totally confused by the registration process.
I was on Techbase, I've clicked "Modify a page" on the right column and I've been redirected to this page. Here you say this is related to userbase and it's suggested to see Techbase, entering in an infinite loop.
This page should also include the information to contribute to techbase or the "Modify a page" link on techbase should point to a different page.
I'm going also to comment on the QuickStart page, which contains obsolete informations.
Replied to the registration process info already elsewhere.
As for the sidebar, feel free to adjust it with updated content. See https://techbase.kde.org/MediaWiki:Sidebar
Since KDE userbase and Techbase share the way on how to modify pages, probably it make sense to keep the link to the userbase documentation without duplication. I suggest to add to the "Relevance" section two subsections: one for userbase and one for techbase where we explain what kind of content should be posted. Does it make sense?