I’m currently in Edinburgh at the semi-annual Shuttleworth Foundation Gathering. One of the other Fellows, Dan Whaley, is working on a killer open source annotation and highlighting tool called Hypothesis. You should absolutely check it out.
I’ve enabled Hypothesis on my blog now (via the companion WordPress plugin!). If you want to make comments on specific words or phrases in my posts (instead of making a comment on the entire post), just highlight a word or phrase and then click on the pen icon that pops up. I’ll be keen to see what – if anything – you do with this new capability. Please annotate posts on their permalink pages rather than annotating them on the front page.
If you want to see all the comments people have made around the site, check out https://hypothes.is/stream/#?uri=opencontent.org. An RSS feed for the stream is on the roadmap, and I’ll incorporate that into the site as soon as it’s available.