I remember this (the trolling issue) was a slight problem when SiteChat[1] was submitted to HN. However, it does add to the sign-up friction, so I'm not sure if the trade-off is worth it or not.
Yeah - we'll need to figure this out. When we posted to r/chrome last week, this was the same comment we got. Then again, we haven't heard this feedback from the, I guess, "non-technical" folks that's been using it... but we will think about this some more for sure.
[1]http://www.chrome-plugins.info/detail/affmlbhoebcjponkmlmoei...