Expand/Collapse More/Less Info buttons are a common concept across the web - wouldn't adding this feature make it easier for users to read those long-text examples?
I am aware that there is the spoiler markdown, but that doesn't collapse down the space, so misses the point of making the rest of it easier to read.
When writing a question or an answer there is often the case where I would like to provide extra information to help the OP or answerers if they need it.
A perfect example would be providing the SQL for the database schema to recreate your problem when posting a question on StackOverflow. Most users won't need to see it when reading your question, unless they have access to a database and want to recreate it. But it is useful info if it is required.
But the problem is this SQL may take up a lot of space. Maybe 100 lines of SQL with a 2 line question at the end. I think this "WALL OF TEXT" turns off a lot of readers.
Some example posts I think could do with hiding text unless required:
Returning top results for events in a competition (the example that led me here)
Making OS X Installer Packages like a Pro - Xcode Developer ID ready pkg (here they have used headers to try and break up the wall of text - good idea, but I think expander would also work)