Is being "emo" a sign of child abuse?

Not necessarily: It is a bit of a "red flag" to have a child to adopts an odd posture like emo, or punk, or goth, or something counter culture. However there are always other things that can lead a child there. Some are just drawn there, others gain acceptance by friends. Some children are outcasts for personality or sexual reasons. Childhood traumas can lead to odd personality quirks, but other things do too.

No: Teens will sometimes do things just to be different (within the crowd of other teens who are "different" in exactly the same way). If dad likes short hair, son grows his long. If mom is conservative, daughter dyes hair pink and purple. A sudden drop in grades, change of interests, or personality change is a red flag that something is going on, but not necessarily abuse.