Chatafs

I was recently asked by someone about the proper pronunciation of חטף vowels. It has always been my understanding that the חטף vowels can essentially be pronounced either way. Take מרדכי, for example. There is a חטף קמץ under the ד. Most people pronounce it as a שוא but I have heard some pronounce it more like a קמץ. However, I recently saw a puzzling line (highlited below) in the משנה ברורה סעיף ה, ס"ק  ב which throws that notion into question. He seems to indicate that the pronounciation of the חטף vowel is like neither of the two. Can anyone shed some light on this opinion of the משנה ברוה and anything else regarding חטף vowels?