It can have that connotation, but the word montony means a dull, drab, or boring state, one caused by endless repetition of the same activity without change.
The word monotone means a flat, droning, unchanging vocal style.
Be mean and annoying back. Or you can rat them out! get them grounded for like 2/3weeks or something! If you really cant say anything because you cant think of anything, then tell him that he's...
There could be many reasons. Constantly liking what other people write and liking everything almost everything on people's wall. Writing gibberish, boring or nonsense stuff on other peoples' walls....