How does combat guarding work?
The role you see when you start combat guarding isn’t important. All that roll does for you is give you an indication of roughly how well you can guard, based on your skill at guarding and whether you’re standing, sitting, etc. The roll that actually does matter is made but not seen whenever someone tries to get past your guard. This roll definitely gets a bonus/penalty depending on what it is you’re trying to guard (e.g. doorways are very easy to guard, so the person trying to get past you gets a big penalty), and probably gets further modified by a few other things too, such as a couple of the attributes of the person you’re trying to stop. Having spoken to a couple of people who are pretty good at combat guarding, it looks like it’s impossible to guard perfectly, so presumably people never have more than 95 success to get past you, and will eventually succeed if they keep trying.