File threads superseded file comments in July 2018. On May 22nd, 2019, we will permanently retire the files.comments.add and files.comments.edit API methods.
Vintage file comments remain accessible and deletable with files.comments.get and file.comments.delete.
On May 22nd, 2019, files.comments.add and files.comments.edit will cease functioning. You won't be able to add or edit file comments.
file.comments.add, in particular, will no longer transmute your comments into message threads.
In consequence, the documentation for these methods will no longer be made available.
files.comments.get and files.comments.delete will continue to function. Use them to retrieve and delete historical file comments. files.comments.get just might be the last place on the internet where it's safe to read the comments. And if it isn't — well you still have files.comments.delete.
If you're still using files.comments.add, your business logic will need alteration to support file threads. Our July 2018 changelog details the migration path to replying to file thread parent messages with [chat.postMessage] instead.
You won't be able to edit vintage file comments with file.comments.edit. As file comments are no longer created, this limitation effects only your ability to edit historically created comments. If you want to edit threaded messages in reply to a message about a file instead, use chat.update.
We'll finish retiring these dusty methods on May 22nd, 2019.
Let us know if you have a comment or concern. Thank you!