We're looking into this issue. We will improve the comments feature to enhance user experience.

Thank Graham for your help!
Hi hallo leo,
Could you please tell us more scenarios about this feature?We'd like to hear your voice.
Indeed, diigo is packed with lots of subtle yet powerful features throughout. Despite we are making full use of time to make diigo serve tons of users better and better ,there are still so many things on our schedule.It's nearly impossible for us to have all the every possible features that one wishes .Our limited time and energy must be given to tasks with higher priority. Sufficient details is needed.

Diigolet does not have the feature of snapshot. It's a simplified edition of diigo toolbar.
Can you download other extensions successfully? BTW,what's the download software you use?
We cannot reproduce the download problem.