Hello! It's been a while. Well, this time I post because I've come across something I'm not sure if is a bug or not. Today I've been working on a comic page meant to be "colored" in grayscale. As it is intended to go for prtinting I decided to work directly in CMYK and simply lock the CMY channels, but I realized this: Channels docker no longer has the channel lock checkbox, only the enable/disable (which, strangley, takes a few seconds to toggle).
I decided to go on and start applying tones. At some point I tried to apply a gradient, but nothing changed, then I checked the layer thumbs and it showed the gradient normally; I thought It was because I wasn't using a pure black color in the gradient, so I moved the CMY sliders in the specific color selector to zero and tried to apply the gradient again, but nothing happened. Just for testing, I re-enabled the CMY channels and this time the gradient showed up, so I'm guessing Krita is making composite black gradients even if I'm using a pure black.
Test it yourselves and tell me if you're experiencing the same behavior: Open or create a CMYK doc, then disable all channels but the black and alpha ones. In the specific color selector write CMY values to zero and then put the K value at whatever percentage you want. Fill any area with the paint bucket or the fill command, you should see your filled area displayed normally. Now repeat the process but use the gradient tool instead of the paint bucket, you should see nothing in your picture, but it you hover the mouse on the layer thumb you'll see your gradient. Again, it seems Krita is doing gray gradients with a mix of the full CMYK colors, even if you turn CMY values to zero. Is this intended to work this way? Oh, I'm using Krita 2.8.2 in Kubuntu 12.04 64-bit, by the way.
EDIT: Also, right after this I decided to convert the document to grayscale to work, but Krita crashes when converting from CMYK to grayscale, and now that I think about it, it's not the first time it happens. I don't have the debugging symbols installed right now, so the bug report wil have to wait a bit more while I install them.

The channel docker toggles the visible channels in the image; to toggle channels in a layer you need to use the layer properties dialog. As for the conversion crash, I cannot reproduce that here. If you can let me have your CMYK image, I can try to reproduce.