Most likely the page was immutable because it was being edited by someone else. But apparently not to fix this problem; the spam link you noticed was still there.
Alternatively, I think sometimes users log in, but are redirected to a page where they are still not logged in and cannot edit. Clicking to log in again usually fixes that (immediately, and without requiring reauthentication).
I've verified that this was really a spam link as you say, and that the correct link you've provided is indeed correct. After double checking that, I edited the page and corrected the problem as per your suggestion (crediting you in the comment history). The link is fixed now.
Ask Ubuntu is not the best place for reporting problems with Ubuntu documentation, but it is an appropriate place to ask questions, including about how to overcome problems using official Ubuntu resources like the documentaton wiki. So I think it was reasonable for you to ask about this here; nonetheless, we'll likely close this question.
Please feel free to continue posting "How do I fix..." questions. However, in this case, it appears your intention may have been to report a problem. Problems with documentation that you're unable to fix yourself can be reported as bugs, as dobey says.
I believe ubuntu-website
is the correct package for reporting bugs/problems in the Ubuntu help wiki, http://help.ubuntu.com/community/, since the other obvious possibility, ubuntu-community-website
is specifically for http://community.ubuntu.com.
Project descriptions:
ubuntu-website
: "The main ubuntu website, the wiki and associated sites."
ubuntu-community-website
: "Theme, bugs, and other resources for community.ubuntu.com"
Other relevant resources: