The reason I think it might be good for especially a novice to have to consciously choose the category is that especially some people in the original suggestion saw question categories as an important structure, the usage of which should be enforced on /all/ users. I do not think it should be enforced, but now that the question bank is hidden in the quiz view by default, encouraging people to use categories at least while creating questions is not harmful - and a dropdown probably does not slow anybody down much anyway. This is not crucial, but may help novices to get started on their dreadful ;) journey to understanding the question bank.

Perhaps a better approach would be to make the category list visually more prominent/attention catching, i.e. the entire list visible in a sidebar, for example.

If you wanted, you could change it to accept a contextid as an alternative to a categoryid, and then make the category dropdown a required field that starts blank (’Choose …’). It is not very hard, but as you say it does involve changing a number of files, which

I don’t think you need a new parameter on the question editing page. That is unnecessarily flexible. Just hard-code the name of the parameter added to returnurl as newquestionid, or something like that. That is a bit simpler.

P.S.
Jos ihmettelet miksi javalla, niin se on suhteellisen helppo ja siitä on yksi peruskurssi tullut luettua.

into any of the services here:
http://www.google.com/search?q=rss+to+email

Or what do you mean?
Thank you for the encouragement anyway.