When I look at my progress, I see how many new characters/words I learned, or forgot, today (or this week/month/year).

Is there any way of knowing which actual characters/words gained the status "learned" and which character/words lost this status?

This probably isn't exactly what you're looking for, but if you go on the "My Words" tab you have a list of all the characters/words you've added. If you click on them, you get percentages of how well you've learned it, when it will appear next, etc.

戴德辉： Thanks for your reply. I am aware of the "My Words" list which is indeed very useful. But, as you point out, it is not exactly what I am asking about here.

On the topic of "how well did I study a given character/word", I mentioned long ago that it would be informative to have the actual number of times a character/word was reviewed, and the number of time the review was correct, and not just the ratio. The skritter team sort of promised to implement it at some stage.

See http://www.skritter.com/forum/topic?id=118568525