It is not a sin to clip the highlights. One has to determine what the primary and secondar elements of their composition are. And if it benefits the primary element/s to clip the highlights of elements in the composition that don't matter, then so be it.
I think the biggest mistake that users of ETTR do is to prevent any and all clipping, and at the detriment of the primary element/s in their compositions.
Clipping done judiciously often provide the best image information/details.
There is an unnamed landscape photographer that shows up in this forum now and then and he boasts that his comps never blow highlights, and he is right, however looking at this vast gallery of excellent comps, one very quickly sees a pattern of blocked up shadows, and way too dim mid tones, but who cares?!? The highlights are never clipped!!! lol
Continue to practice ETTR, and shoot raw, and never, never, never judge exposure by looking at the image on the camera's LCD display...it lies too much....better to ascertain exposure by looking at the histogram. However the blinkies on the image displayed can be helpful to show areas of "possible" blown highlights. And eventhough you may be shooting raw, nuetralize/turn off all in-camera post processing, like contrast, saturation, sharpening, that sort of thing....nuetralize/turn off PictureStyles, which are the stupidest "feature" Canon has given us...keeping these on will only effect the tiny jpg that gets generated in-camera for the sake of displaying the image on the camera's LCD...it does not effect the raw and since it doesn't why allow the camera to "deceive" you? Also, never try to expose so that the image looks "right on"....often a correctly exposed raw image will look flat, over exposed, lacking contrast, lacking pop, and more often then not, this is a very good thing; a good foundation to build upon during post process mastering later on the PC.
One more thing, when shooting raw try to get the WB as close as possible because it's value will effect exposure, even if WB can be tweeked later for raw images. Use color space ProRGB as it is the widest.