I think the basic question ought to be: what type of normalisation calculation does MB perform:
- peak normalisation, or
- loudness normalisation
The former just requires a search for the biggest sample in a file, and the replay gain is then merely a simple gain setting to bring that sample to some target level (which might be the FSD for the bit precision of the samples, or some value X dB below that).
The latter requires a more complex computation of 'loudness', which is a psychoacoustic perception, not directly related to a simple peak value.
A track with a single sample at FSD with all other samples zero would give a peak normalisation replay gain of 0dB (with a target of FSD), but would result in a large loudness normalisation replay gain, attempting to produce an average track loudness; that would cause the single FSD sample to be clipped during the playback levelling. Clipping an FSD sample to FSD wouldn't be noticeable clipping, but, for a more real-world track, it might well be, depending on the peak-to-mean ratio of the track.
So, if MB uses a loudness normalisation function, it might also note the peak value in the track, and determine whether the computed replay gain would cause that peak value to clip. Personally, I would want to avoid any samples clipping, so I would hope the clipping detector would operate on that single peak value. This would also be more computationally efficient to implement, as you would not need to perform playback levelling of all the samples in the entire track.
I would not recommend letting digital music clip during recording. Digital clipping simply hits a hard end stop; it is not forgiving of overloading like tape recording is, which results in a soft clipping due to saturation of the magnetic tape.
Unless hard digital clipping is a 'sound' you are going for in the style of music you play (some sub-genres of metal). But you can easily add that effect, to a selectable degree, in post-processing of the recording. Trouble is, you need to set your recording level at the start of recording, anticipating the peak input level.
Hard clipping on CDs came in with the 'loudness wars', which most people agree resulted in horrible-sounding recordings.