When any of the sailor senshi are knocked unconscious...

[Crescent Pulsar S]

Did they return to their civilian appearance, or remain sailor senshi? Examples can be from either the anime or the manga. The one example I can think of, in the manga, I think they were dead, and I can't readily think of another place to check since I'm so focused on writing right now.

[Spica75]

Based on anime, remain senshi without the slightest doubt. Makoto gets knocked into a garage door and apparently goes unconscious without any change for example.

And when they die, no loss of senshi-ness as i can recall.

[Cheb]

I confirm.

Can't say the same for manga, though... hmm... No. I think, they remain Senshi and super-durable as well. There is one scene where they tire out while levitating several dozen meters above ground. They then lose consciousness and crash-land on concrete for no damage.

[Spokavriel]

The only time I can remember a forced de-transform was when Usagi's broach got crushed.

[Spica75]

The only time I can remember a forced de-transform was when Usagi's broach got crushed.

Yup, same here.

[Crescent Pulsar S]

Thanks for the feedback, guys. I wanted to see if a certain scenario was feasible, but it looks like I'll have to do without it.

[Cheb]

The only time I can remember a forced de-transform was when Usagi's broach got crushed.

And the black dream hole that sucked their magic out. That was the second case.
So, no. Not until someone attacks the focus crystal on their chest (hmm, an analogy to the angel/Eva cores here) or an anti-magic zone happens.