1. The extension ONLY tracks the TOTAL number of times an article is staged, NOT what has recently been staged. This forces the admin to look through the entire list to see is there is anything needing "looked" at and approved or reversed. There is no "new or recent cue" ... so if you are using this extension as part of a wiki-style setup in Joomla with lots of updates being performed by lots of different registered members (as in my case), this would cause a ton of frustration. In fairness though, I don't believe it was designed for that particular environment (hence my good rating still).
2. As I was testing the extension, I noticed once where the extension did NOT portray my edits correctly in the staged version awaiting approval. Lines were crossed out that were never actually deleted. This concerns me a bit, and makes the extension a little untrustworthy. Is it showing me the "true" updates or not?
3. Versions and Workflow on the front end was a bit difficult to understand what was happening. Sometimes it didn't show other versions at all, though this may have been my particular permissions in need of adjustment. Also, the tabbed css was off a bit with my themes. Should probably get rid of the tabs and go with something more straight forward and functional; not as pretty, but this would then work better with other themes.
I believe with some tweaking and more testing this would be a really nice extension.
Thanks for the review.
Item #1 is actually not correct. If you click on the Workflow button you will see the revisions ordered by date, including the content of those revisions.
Re #2: We use a open source HTML Diff, which is about as good as it gets. HTML Diff is non-deterministic, test changed to test actually looks like the string "test" was deleted.
#3 is always tough, e.g. themes with overreaching CSS are freely able to manipulate our layout.
Your question is probably answered on the forum already, as it's too simple. Either disable the Joomla! reCaptcha plugin and enable K2's built in or the opposite. Both will work. If they didn't, then maybe some other system or user plugin is to blame. If I were you, I'd disable Joomla! reCaptcha, because K2's can also be hooked up with StopForumSpam, in which case, real human spammers are 95% of the times caught and blocked.