You were not fighting xenos when I marked you. It marked you several minutes prior to the engagement, and the xenos nearby were not a threat given you had several marines with you. As far as the logs tell there were only two xenos nearby, which I don't believe constitutes as the frontlines, just some random skirmishers that were near that road. I made sure that when I attacked you, you had full health and weren't being pounced on or dragged off or anything along those lines by either of the xenos nearby, given by the time I approached those xenos were retreating and weren't looking to engage in the conflict. If I did join the attacking, those xenos would have had logs of attacking you or your allies.