A long Talk comment gets collapsed automatically if it is:

• a long comment that is a part of a collapsed Talk discussion;
            
• a single long comment, and:
  • its length exceeds the page length, or;
  • in its expanded state it interferes with the place of another talk;
    
• a long Talk discussion that consists of 2 comments, and:
  • which length exceeds the page length, or;
  • which in its expanded state interferes with the place of another talk.
    

To expand an inactive collapsed Talk comment or inactive collapsed discussions, which first or last comment is collapsed, select that Talk comment or discussion.

In active Talk comments and discussions you can use the 'Show less' and 'Show more' buttons to collapse and expand long comments.

When you click somewhere on the page or select another talk, your long comments get collapsed again.