Is there still a question here?
To restate what I said before:
Any new message added to a thread will cause that threat to move "to the top", regardless of what text appears in that message.
That may be a trivially short message, consisting of a single letter or maybe even just a "." (period).
Beyond that, you might think it useful to provide some explanation to the reader as to what the bare minimum "new message" is all about, which is what some folks try to do by posting a message composed solely of the three letters "TTT".
Of course, we frequently get questions such as the one that began this thread, so apparently a message containing only the three letters "TTT" doesn't necessarily convey much more information than a message containing only a "." (period).
Bottom line: Such a message serves to indicate that the author posted the message solely to kick the thread "to the top", typically as a reminder that some element of a previous post remains unresolved. The reader may want to review the entire thread.