I have noticed that comments are expanded in a different way when I click "see more comments". For example, if an answer has 10 comments, on loading the page it shows only limited comments with a bottom view "View 4 more comments". But the comments are getting expanded in a non-linear manner as the hidden comments are being shown between the existing comments when I click "View 4 more comments". Is there any specific reason for that or is it designed in that manner?
When there are many comments, only part of the comments are visible.
In attempt to show the most relevant comments, the sort is made by the comment score, then they take X top comments, where X is defined per site. (Maybe it's explained somewhere, but it's not the topic here.)
So, for example, when there are 8 comments total, with scores of 3, 6, 1, 0, 0, 7, 9, and 0, and the site showing only three comments, those with score 6, 7, and 9 will be visible by default. When expanded, the sort is only by date, so those comments with top score will "jump" into place.