Applications of 6MSJ in combat
Continuing on danshu_'s article, I'll try to explain how the 6MSJ works in combat.
And how to counter one of the best skills in the JY canon.
Part 1
To project a 'qi' sword externally outside the exponent's body require very high levels of internal energy and inner power mastery to support such skill. There are two main ways of using this sword skill, which are to generate and sustain 'qi' sword(s) using the fingers (i.e. lightsaber style) or to shoot out streams of energy in pulses or bursts (i.e. laser beams). (Such swords are more likely to bore a hole through an opponent's sword rather than break it.)
Sustaining 'qi' swords externally (in a 1-way current mode) requires extraordinarily enormous amounts of internal energy and concentration which an exponent may not be able to support throughout the duration of the combat even if his inner power level has hit the limit (Level 10).
A way to conserve energy and use the 6MSJ for as long as possible would be to circulate the energy externally (in a 2-way current mode) so that the exponent loses little energy to the surroundings. But in this case there are 2 disadvantages. One is that the range is drastically reduced. In the 1-way current mode, the range is much further as the exponent can just project his 'qi' to his maximum possible range and of course the intensity of the energy stream would decrease with the distance away from the exponent. But for the 2-way current mode, the intensity of the streams would be uniform throughout so that the energy can be circulated properly, so in this case the range of the sword(s) is limited by the maximum range for the exponent to bring his 'qi' back. The other disadvantage is that such a method is very risky. If an opponent is strong enough to interrupt the current flow, the exponent might suffer from a 'fire deviation' which may endanger the life of the exponent.
Another danger of projecting the 6MSJ as external sword(s) is the risk of crossfires, which is less likely if the exponent is extremely skillful and careful with his fingers. In the event that the fingers are not aligned correctly, the streams of energy may criss-cross and cause some undesirable results. If the streams are Yin and Yang they would probably just cancel out if they intersect. But if they are Yang-Yang then an explosion may occur and injure the exponent as well as anyone else in range. For the Yin-Yin case the exponent might suffer a negative feedback and get a fire deviation which may damage his internal organs.
The safest way to execute the 6MSJ and also to conserve as much energy as possible would be to project out the 'swords' intermittently, like aiming properly before you shoot because you don't have many bullets. Using the 6MSJ this way is effectively shooting out streams of energy in bursts, which resemble those laser blaster guns in Star Wars.
Part 2
If the exponent using the 6MSJ is not very skilled, it's not very difficult to defeat him. If the exponent tries to sustain the 'sword(s)' throughout the combat, the opponent has to do would be to stand outside the maximum range and wait for the exponent's energy is fully expended and he would then be able to defeat him effortlessly. :D
Or if the opponent can try to distract the exponent to make him lose his concentration, causing the 'power supply' to be interrupted or causing the exponent to crossfire. If the opponent's internal energy is comparable or superior to the exponent's, he can try to use his own internal energy to disrupt the flow of the stream(s) of energy in a 2-way mode or simply generate a 'qi' shield to neutralize the exponent's energy stream(s), which is more appropriate for the 1-way mode.
If the exponent is more highly skilled, it would obviously be harder to defeat him, but it's by no means impossible. Though the streams are invisible, an experienced opponent can 'feel' the streams because they cause slight alterations to the environmental conditions like a slight change in temperature and pressure. Experienced opponents would also be able to sense when an exponent is about to unleash the 'qi swords' through his finger movements, breathing, posture, etc. and engage in combat as though they are armed with infra-red goggles. Armed with all this data, the opponent would then be able to execute a Mace Windu-style neutralization of this extremely powerful sword skill.
Nothing is invincible. Nothing is impossible. ;)