Hey there,
This is almost the same as your blogs plugin, so should be a fairly quick fix (you've done it already for that plugin): http://www.oxwall.org/forum/topic/42737
The URLs are inconsistent and can be accessed through:
/articles/article/22/article-name-here
/articles/article/22
/articles/22
The first one (with key words from the title) is desired and should be the default. Fixing the links in the widgets, user profile, and articles/user/USERNAME to point to the first one should be good enough, but the best solution is to either redirect everything to the first one or even just add rel="canonical" that points to the first one -- so access to the other ones won't be flagged as duplicate if they point to the first one canonically.
I noticed your blogs plugin redirects the other links, this is perfect for the articles plugin as well.