Dwig
Well-known
That depends on your editing methods, and simply opening a jpeg certainly doesn't lose any data.
Opening a JPEG doesn't cause the loss of data, true, but data was lost when the camera created the JPEG from the sensor's RAW data. That lost data can not be recovered.
One aspect of IQ where post processing a RAW file can easily best an in-camera JPEG is in fine detail retention when, and if, the file is to be printed and the intermediate processed file is a non-lossy format (e.g. PSD, TIFF with other than JPEG compression, ...).