I have some tartan fabrics made with a tuck in selvage, and it is perfectly neat and acceptable.

It is done so that each thread of the weft is cut, rather than being continuous with the next thread in that colour. The end of the thread is run back into the fabric so it effectively makes the fabric twice as thick just at the very edge.

You'd need to get very close to see that this was the case, and perhaps even have to feel it to be sure. The tiny tufts of the ends can be felt, but they must be pressed down in processing, because they are not very obvious, at least on the fabric I have.

I have read that one firm has got custom made looms which make a true kilting selvage, which is commendable, but for most purposes a tartan with a tucked selvage isn't going to be in any way detrimental to the kilt.

Anne the Pleater