Why is the discussion page not a standard Talk: page but some confusing "Browse topics" thing?
Several months ago there was a change to the talk page design. For talk pages that were created after the change (such as this one), while for the old ones the system was not updated such that adding a topic merely caused a header to be added, and replies need to be made by manually adding subheaders and signatures.
This one with the 'Browse Topics' is the standard talk page format for the wiki now, the others are in fact not functioning properly. To update them would require manually deleting the talk page, causing the wiki to generate a new blank talk page in its place with the correct formatting.
If by 'standard' you mean old pages such as Talk:Cover, then in fact these are broken as they do not support proper replies, and manually replying by editing the page isn't a good idea to go.