Short comments (additions, corrections, recommendations) can easily be tagged onto a documents (files, new items, etc). Go to the appropriate folder, select its contents tab, and then select the document or other item of interest. An add comment button should be available below your selected item. Select add comment. A form should appear, allowing you to type your comment. (Or, you can copy and paste from your word processor.)

Prior comments will be presented, if any have been entered. You can reply to them individually.

Comments are most easily collected using your computer's copy and paste abilities. See DownloadingDocuments for more details.

If you select a folder's view tab, rather than its contents tab, you should still find the item you seek. However, if it is a file, eg, an uploaded word processor file, downloading will begin automatically: there will be no opportunity to add comments.

Wiki pages are inherently designed to accept commentary. There is little point in adding a comment to a Wiki folder. (Overall comments should probably be added to the first page.)