Me too is a common Comment in online Discussions, incidicating that the commenter agrees with the original poster (or with a previous commenter).
In some communities, "me too" responses are unpopular, as they lead to high traffic with little original content. This was particularly the case on Usenet and Mailing lists in the mid 1990s, when an influx of new community members, unfamiliar with Community norms, flooded discussions with "me too" posts.
However, in some other communities, it is considered good practice to let people know you liked a post, even if only in a few words. This avoids Warnock's Dilemma, in which the original poster may be unsure what to make of silence. There are some more modern ways to phrase "me too" to indicate agreement while not looking like a Newbie: "THIS." and "+1" are two common examples. Some discussion platforms offer a Like mechanism to indicate that you liked a post without having to actually comment on it.