what can the dot command repeat, exactly?

Question

Vimmers know that . can repeat simple changes. I tried to build a list of what can be repeated or not, but is there a list?

I tried to list what I know

Answer 1

Insert mode expression register is NOT re-evaluated

Example: If you want to sort following inline lists of numbers,

 first 3,2,17,198,232,1,999 and some other text
 second 1,2,3,71,98,4,5 and some more text

consider these two ways using the expression register:

1. ciW and then =join(sort(["]), ',')
2. ciW and then =join(sort(split(expand(@"), ',')), ',')

If you try to repeat either of them for the second line with ., vim simply enters again the same list from the first line. This might be expected by others but I was hoping that for the second way the expression register would be re-evaluated.