It depends on the sword. During the Renaissance, the cloak and cape were like the dagger and the buckler, used as a supplementary in the offhand to the rapier. It could be used for defense, to distract, lock up an opponent’s sword, and other uses.
If you didn’t know how to use a cape, then it would be liable to get in the way. Get caught on the arms, tangled in the legs, distract you as much as your opponent. The cape and cloak are period clothing, much like a jacket would be for us today, which means if you’re a man (or woman) during the Renaissance you’ve got a choice when the time comes to fight or duel about what to do with your clothes. You can discard it, risk losing it if there’s no one to hold it for you, or use it as part of your defense.
If there’s one thing that is worth thinking about when you’re setting up your fight scenes and your characters it’s the concept of “using what you have”. Combat is joined with culture, it isn’t an abstract or separate. One uses the tools in their environment, designs their weapons around where they’ll be fighting and the threats they’ll face as much as how. Your character’s clothing, their culture, fashion choices, all reflect back into their defensive options (or lack thereof).
The cape was one of the common accoutrements, so it got used by some fencers when they were caught without their buckler or their dagger.
Humans utilize tools well, and adapt well. When looking through the links pay close attention to why the cloak works and how it aids a fencer as a combat tool. This will help you when looking back on modern clothing or other day to day items you may never have considered before that easily become natural extensions of a fighting style.