When there are several comments some of them get hidden, which I don't mind, except when comments in the middle are hidden and I don't realize it till I get to the end. Then I have to unhide the comments and try to figure out which ones I haven't read.
The comments stay in order as they should so you can follow them but when you hide random ones in the middle you can loose the context of the comments until you unhide them all.
I have a couple of ideas that could help with this.
Put the Show X more comments at the top of the comments instead of the bottom
Put some indicator that there or hidden comments between these two
Comment this is the first comment Comment this is the second comment ... Comment this is the fourth comment, comment three is hidden indicated by the dots Comment this is the fifth comment ... Comment this is comment number nine, comment 6, 7, and 8 are hidden
Where the dots equals some indicator that there are hidden comment between two comments
Finally you could highlight the newly shown comments when you hit the unhide comments link like you do when you post your question.