Use English. Only exceptions are Languages, where you can use language appropriate for each page, but please include also information in English.
Anonymous editors and editors without confirmed email and without enough good edits have to pass captcha test. This is needed because of increased amount of spam probers. There are effective ways for blocking bots to enter URLs, but they just probe whether they can edit wiki by adding random letters sequence and this is quite hard to detect.
Creating pages is not allowed right after registration to prevent spam. Currently you will be be able to create page 7 days from registration.
We regularly check recent changes on wiki. If we find spam, the IP will be blocked for 3 months and any URL is added either to local Spam blacklist or metawikipedia:Spam blacklist. If spam has been entered by user, it will be blocked forever.