The encode use flag enables/disables two independent features in k3b: 1) It enables/disables mp3 support for the Rip Audio CD feature. 2) It enables/disables the dependencies for the Rip Video DVD feature. These usages should be separated into two different use flags. My suggestion is to use the "mp3" use flag for (1) above, as that would make it consistent with the vorbis and flac use-flags. There is a workaround to use (2) but not (1), you just have to install transcode and sox manually. However, if you want (1) but not (2), the only solution is to patch the ebuild. Personally, I'm only interested in (2), so I'm using the workaround, but I'd prefer if it was properly fixed.
I don't think its really going to help much since the encode use flag only enables one use_enable option. Whether turning that on/off disables both, I'm not sure. But we can't just rename the flag to one of them if it still covers both.
Closing bug