does the 757 ever board through both 1L and 2L
 

From experience flying the 757, sometimes it's 1L, sometimes it's 2L. Favorite config for F pax is to board 2L and exit 1L. Anyways, was wondering are there any airports that are capable of boarding a 757 through both 1L and 2L simultaneously or is it not feasible?

It is feasible but not really practical because it is a single aisle aircraft. No point having two feeds into a single channel.

It would be great if they did that, but I suppose a separate ramp for 22(12 on the left, 10 on the right if I recall correctly), is quite over kill.

When BA had the 757 boarding C through 1L and Y through 2L was quite common at outstations where steps were used. When one door was used with a bridge it was almost always 2L so you could turn left when in C.

In the early day of the 757 both doors would be used when boarding by stairs. F at 1L and Y at 2L. Some charter carriers with all Y cabin 757 would board 1L and 2L by row numbers.

Very common in Europe is to board 1L and 4L on a 757 (eg Monarch Airlines)by steps, and likewise for A320/737 etc to board by both front and rear steps. At London City it even happens on BAe 146/RJ aircraft.