I can reproduce this with every discussion which is having more then 26 posts. eg:
I also have tested a lot of different readers in order to be sure that's not my fault. but it' is not necessary to use a reader - also using the rss button in the browser shoes only the first 26 posts.
it is working with discussions under 26 posts but stops over 26 posts
would it be possible for you to check this and give me a short reply - I think it is better to ave a second opinion