Well, just a quick look on wikipedia says:
When referring to a person's personality and attitude, most definitions of emo hold that an "emo person" is candid about their emotions, sensitive, shy, introverted, broken-hearted, glum, and often quiet. Emo personality is also often connected with writing poetry, which addresses confusion, depression, loneliness, and anger, all resulting from the world's inability to understand the author. Emo poetry uses a combination of any of: a highly emotional tone, stream of consciousness writing, a simple (ABAB) or nonexistent rhyme scheme, references to the flesh, especially the heart, heavy use of dark or depressing adjectives, concern over the mutability of time and/or love, and disregard for punctuation, grammar, and/or spelling. Themes such as life is pain are common.
Some definitions of emo hold that typical "emo persons" are likely to inflict self-injury, most often by means of cutting, burning, or otherwise mutilating themselves.  Some assert that it is cool within the emo subculture to pretend to be suicidal and self-harm, or that participants self-harm purely for personal enjoyment.
Emos are also stereotyped to use depressing Internet screen names that sometimes contain straight edge X's, often using ironic sloganry, a poetic sense or cliché (eg. xmourningafterx).
In the years since emo music's rise in popularity, both emo music and emo subculture have attracted sometimes severe criticism. The term emo itself is sometimes used pejoratively, to suggest that the target is "overly emotional." Emo in general has been characterised as a fad which will be discarded and forgotten in the near future. Emo music has also been compared to the teen pop of 1990s boy bands. Critics cast the music as lacking any artistic merit, the fashion as "embarrassing" and members of the subculture as imagining or pretending that they lead harsh, painful lives when they actually live in comfortable, upper- to middle class homes. Members of the emo subculture are portrayed by critics as melodramatic, self-pitying teenagers who pour their efforts into writing bad poetry and spending a great amount of time on MySpace. The current emo subculture has been called a "sad caricature" of what it once was. Critics have gone so far as to contend that the emo subculture or emo music are likely to cause youth to commit suicide. The backlash against emo music and subculture has become so prevalent that it may itself have become a cliché: one commentator notes that "hating emo kids these days is as hackneyed as emo itself."
But I think you need to really evaluate if this is a super-serious behavior on the negative end of this sub-culture or if its just fitting into a crowd.