In systemsettings → file associations I'm trying to set khtml as the default embedded viewer for text/html, but whenever katepart is included in the list it always gets the highest priority.
This means that all webpages opened in Konqueror are viewed in katepart by default. If I move katepart down in the list my setting is ignored and it is still the default viewer. Removing the katepart entry makes khtml the default viewer again, but I want to have katepart as a secondary option.

Why does katepart always get the highest priority, regardless of what I do in systemsettings? Is there any configuration file that's overriding everything?

I'm running KDE 4.2.4 on Gentoo.

It is possible that the file is matching another mime type, or Konqueror needs to be restarted for this to come into effect ( try running kbuildsycoca4 --noincremental also )

Running kbuildsycoca4 --noincremental while systemsettings is open immediately bumps katepart to the top of the viewer list. It doesn't seem to change anything else. Granted, I don't really know what it was supposed to do. Restarting Konqueror does not solve the problem.

If you create a new user, can you reproduce under that user?
If you cannot reproduce, ensure the entirety of ~/.kde*/ is owned by your user, and has valid permissions ( 750 / 700 )

I was able to reproduce the issue under a new user.
Here's what I did:

After creating the user and logging in, open systemsettings → file associations
Click on text/plain and go to the embedding tab
Remove kwordpart from that list (I have Kword 2.0.2 installed)
Click Apply.

After doing this, html files are always viewed in katepart.

If you just move the KWordPart down, does the issue occur?

bcooksley wrote:If you just move the KWordPart down, does the issue occur?

Yes.

I do not believe the KHTMLPart supports text/plain files, so it likely forwards them to KatePart. Can you check the associations of text/html?

I'm not sure I understand what you are asking. Sorry if I get it wrong.

Upon creating a new user, the associations of text/html is khtml, katepart and kwordpart in that order.
After removing kwordpart from text/plain, it is also missing from text/html and katepart is always at the top unless I remove it from the list entirely.
Html files will only open in khtml by default if I remove katepart from either text/plain or text/html.

I've noticed that svg+xml behaves in the same manner. There might be other mimetypes that are affected as well, but I haven't checked thoroughly.

Quite interesting. This is definitely a bug, which needs to be filed at bugs.kde.org aganist kdelibs. In the meantime I simply suggest you "remove" items by placing them to the bottom of the list.