[Note: I don't know if this is a general comment about the Stack Exchange network at large or something that is controllable site-by-site.]
When a comment thread gets too long, stack exchanges seem to use a rule for determining which comments are shown and which are hidden (perhaps chronologically by "has greater than 1 upvote").
I find hidden comments a bit annoying, especially on mobile. Typically, there's a flow to the comments, but reading them as shown (without clicking "show X more comments") gives me just some highlights. While comments aren't meant to serve as a secondary conversation between members, they sometimes are, or they hold multi-comments (i.e. parts 1-3) from a single user. Having to click to show the non-upvoted comments is awkward from a reader's standpoint. On mobile, comments suddenly appear above and/or below your current view.
So, why do we have this functionality? Is it really helping readers by showing them just the most popular comments? And to the main point: Is there a way to automatically show or hide all comments when a page loads?
[Update] This type of question apparently has quite a history on the Stack Exchange network. See here and here and here. The short answer is that you can change some functionality for your own computer if you're willing to do a little bit of coding. So, carry on, then.