That's a good question, Steven. My answer is conditional, and based upon who is walking home and what time of day. There have been some robberies/assaults of both men, women and youth associated with the light rail. If you've got headphones in your ears, your iPhone in your palm, and a laptop bag, then you're making yourself a target. You can take measure to make yourself less of a target.
Besides light rail, you could also be robbed walking home from a bus stop....or have your car broken into while parked at your home if you leave anything of value visible. Crime is everywhere. If you take precautions, don't walk alone at night, leave valuables at home or out of sight, then you increase the odds you won't be a victim of crime.
Columbia City is continuing to evolve, and the light rail is evolving as well. More people are discovering Columbia City, and the great home values in 98118, and there is a new energy in the community. Columbia City is a good place to invest and I don't think it's any less safe than many communities in Seattle. I hope this information is helpful to you.