I think my friend performed this by accident today. For those who wonder, here's how it looks from the other side:
Bascially it does show the fake indicator, just like with zone attacks.
My friend also plays with mouse/keyboard, and occasionally we have network issues (like when animation plays particles effect from block/parry but then hit goes through).
Oh, now I know why I wasn't able to reproduce it. I misread that you need to change guard direciton before the first attack (which is going to be canceled). It was this video https://www.youtube.com/watch?v=zUJhcQMhZ_M that helped me realize this.
With that knowledge I now can reproduce it with Nobushi.
So it looks like soft feinting light attacks (at least) still gives the parry indicator as shwon in that vid above with teh nobushi and warden. The fact it still shows the parry white flash tells me that will be very powerful. Giving fake parry windows? So even if you read the move right and try to parry you'll fail and get smacked by another light. Feinting a heavy here I believe won't save you. I don't think you even have enough time to parry feint.
After realizing I was initially doing wrong, I've finally done some soft feints in practice mode. The timing is definitely strict, but what annoys me about this bug is the reason why it wasn't working for me at first. I was switching stance once, not twice. The fact that you have to switch stance *twice* to get this to work is a clear sign that this was not intended. What I don't understand is why it works after two stance switches, and not just one. Does the game engine just go full ****** after more than one stance change and forget certain actions should be impossible?
What's funny is that the bug itself, is buggy. Maybe it's because I play as a Lawbringer, but even when I get a soft-feint off, sometimes it's delayed in execution (which completely destroys any usefulness this bug may have when that happens). I've said it before, and I'll say it again; if soft-feinting is accepted by the devs, they need to tweak it (if possible) to be more user input friendly (and remove the buginess from what is currently a bug; funny, that). Otherwise, it will remain as a potentially useful, but janky tool for players to use. If that is the case, it needs to due in a fire.