I'd add some {} in here to make it more obvious which "if" the "elses" belong to

Indentation messed up?

I see compiler warnings in all lines using mtx_tranf. It is an array of float*, where all the following lines of code assume float[4][4]. I'm not sure if there's a truly elegant way of handling this, but this slightly convoluted variable declaration allows the code to build without warnings or having to use casts:

				float (*(mtx_tranf[3]))[4][4];
				mtx_tranf[0] = &rv3d->twmattrans;
				mtx_tranf[1] = &rv3d->twmatrots;
				mtx_tranf[2] = &rv3d->twmatscale;

Later, the calls to the copy matrix functions will then need to dereference the pointers in the array:

				copy_m4_m3(*mtx_tranf[i], mat);