The program works with PCM Wave format internally.
Does this mean if an MP3 is decoded to WAV, cropped, and then re-encoded to MP3?
If so, surely this means further degradation of the original file?
[Of course I understand that other operations such as fades would necessitate re-encoding since the underlying data is actually changing!]
For some of the editing commands involved, decoding/re-encoding is unavoidable.
This program works in a way that the output quality should be as high as possible while still keeping a reasonably small file size.
After all, most of us are not that picky as professionals, who are unlikely to use a tool like this.
BTW, the latest version lets you save decoded MP3 to the lossless WAV format.