To answer your question directly yes you can connect a stereo mic directly up to a mono input without causing damage. Worse case scenario is it won't work. Next worse case scenario is it will work but you will only get one channel. Most likely scenario is the soundcard's mono connector is designed to touch the ring and the tip and short them together creating one channel that is the addition of the two channels from your microphone You see The tip and ring on a stereo headphone jack are the two channels and the sleeve(the part closest to the wire) is a common ground.
In theory the two microphones may fight each other causing distortion, but looking at your microphone's schematic I can tell you you have a well designed preamp built in to the microphone that will prevent this. If you want a studio quality solution what you do is you make or buy a mixer. This can be made with a chip or two(I suggest an OP amp designed for low noise, low distortion, small signal audio applications) and a few resistors or a couple potentiometers if you want variable amplification/mixing.
I found a schematic for your microphone.
Your microphone is self powered. You can see each microphone element is powered directly on one side. The other side is connected to a JFET(Junction Field Effect Transistor) . This transistor is operating as a buffer and voltage gain section. It has a very high impedance(>100k ohms) and a high voltage gain. It however has a high output impedance(guessing around 10k ohms I haven't done any circuit analysis). This is undesirable. So the JFET voltage gain/buffer section is followed with a BJT(Bipolar Junction Transistor) in an emitter follower configuration. This type of amplifier has a voltage gain that is near 1(98% or so is normal) but it makes a good output buffer due to low output impedance.
source: electrical engineering classes at an ABET accredited school