And it's not pronounced any differently, right? It's strictly a spelling thing?
Older and more formal Klingons tend to pronounce the glottal stop, or any doubled consonant, twice, or once but double length, while younger and less formal Klingons tend to reduce doubled consonants to a single consonant. (This information is from the book Klingon for the Galactic Traveler.)
This course will only give you the formal versions.
Effectively it is not pronounced any differently. It is possible to release a little air between them to produce two glottal stops, but it is very rare to hear anyone do that. So it's mostly a spelling thing. But part of the reason why it's a really important spelling thing is that Klingon syllables follow very strict patterns that actually help to read Klingon quickly and removing one of the glottal stop markers would throw off the pattern and make Klingon more difficult to read for those who are used to it.
It's very difficult to execute even one glottal stop after the syllable maw, let alone two. The final sound of that syllable, "w", is made by the lips, then you have move all the way back to the glottis for the glottal stop ... it just feels completely wrong from a linguistic standpoint. :-)
I guess the Klingon language doesn't have the process of assimilation. Oh dear, I fear I'm treading far too close to a Borg pun here. ;-)
Yeah, on second thought after posting that, I realized it wasn't quite as bad as I was making it out to be. There are some sounds that are difficult to make in close proximity to each other because they're in different areas of the mouth, which is where the linguistic process of assimilation comes in - sounds moving forward or back in the mouth, for example, or becoming voiced or unvoiced, because of the influence of another phonetic component either directly proceeding or following them. But actually, a glottal stop is probably one of the easier sounds to stick into the middle of a word without it really affecting the sounds around it. I was just having trouble trying to pronounce mamaw''a' at the time. :-) Thanks for the comment and example.