Too many people confuse "glow" with actual light effects - something achievable with any lens from any manufacturer. The glow people (in the know) keep referring to is directly linked to spherical aberration in lens design. A few manufacturers, namely Leica and Minolta, tapped into this as a major design element of their "look." Said look died at Leica when Walter Mandler stepped down from optical design and Peter Karbe took over.
If you want the original look, don't buy new Leica lenses.