Most posts on this site now accept submissions for additional notes. If something in a post jogs your memory — reminds you, perhaps, of a related experience or something in a book which sheds further light on the subject, we invite you to make the connection for other readers by submitting a note for permanent publication alongside the original post.
That said, if you do get a comment published here, you should add it to your resume.
Keep in mind, you are not simply “commenting” on the original, but actually being invited to try adding to it. Be authorial; be original, be clear. There is no limit on length as long as your writing justifies it. If we see promise in a submission that nonetheless contains non-trivial shortcomings, we may contact you with our concerns and work with you to shape the thing up.
Note that we don’t display the time/date of published comments (although they do appear in order of publication), so readers will not know what year you wrote unless you need to mention it. Avoid statements whose relevance will expire with time – think of writing for a limited-edition book, not a fish-wrap newspaper.
Simple statements of opinion do not have much chance (even if they are nice opinions!). Obvious marketing and incivilities will be shot on sight.