Proliferate trigger doesn't work for players

[travolter]

I found a few time ago than proliferate trigger is broken. It doesn't put counters on players.

Replika wrote at Slightlymagic

Volt Charge, although being listed as an instant, is only castable at sorcery speed. I also didn't figure out how to proliferate a poison counter onto my opponent with it (it works with -1/-1 counters on creatures though).

In this card, I use the triggered ability to add proliferate. However, activated proliferate ability works without problems.