In response to the original question, we first have to know what each dignity and debility means forgetting anything we have ever learned of scoring and weighting. The texts, especially those of later authors are replete with analogies of what the dignities mean, but I find these to unhelpful since they promote a hierarchical view of the dignities before telling us exactly what they mean.
Now the following is my own understanding of the triplicites and may or may not mirror the ancient astrologers' own. Valens and Dorotheus both echo a tradition that advises us to look to the triplicity lords of the Sect Light to see the level of support a native gets in each period of life. This for me is key; support. It is my understanding that the triplicites show support. A planet in its own triplicity is supported, especially when aspected by those who would support him/her i.e. the fellow members of the triplicity they rule. It seems to me that everything that the triplciities stand for relates back to support: the support of the native through the king or queen (The Sect Light); the support each ruler itself has when predominating (just because it is a day chart, Jupiter and Saturn do not do nothing in regards to the rulership of triplicities, they just take a supporting role), no planet rules a triplicity on its own, it always has support; the triplicites are linked by trine and the trine is the aspect of support, friendship and harmony.
A planet then in its own triplicity is suported and with friends. I think we all know how much difference support and friendship can make to the success of our endevours. Of course, if we have bad friends (malefics in bad states), or friends unable to help us (benefics in bad states, or fellow rulers not aspecting the planet), this can harm our actions. So each chart must be read individually to see the level of support a planet receives. This should be done in the basic, traditional manner
As for fall, this is the opposite of exaltation. I think the analogy of being an honoured guest is about right and conveys what we want for this dignity. The opposite of this is to be ignored or shunned, in a place where no-one cares about you or notices you. This is difficult as it restricts the basic nature of the planets. Benefics will do less good because they cannot make full use of their own resources (for one thing they are not in their own domiciles and, worse, they are in a place which causes them to be ignored, thus not being able to use another's resources) while malefics will do more harm as they are unseen and unrestrained and thus more destructive.
Putting it together for Mars in Cancer say, ignoring sect, we have Mars as a malefic in fall. He is being shunned and ignored and is given free-reign in a place where he is not restrained. Since the Moon rules him and is also a triplicity lord, her influence is of vital importance as to how destructive he will be. If she and Venus both regard him from good places, we can say he wil be a bad, low-down, shunned man with good friends - their goodness will restrain him somewhat, especially the Moon since he is in her house and lives by her rules. A bad man in the company of pure angels is less likely to be bad while they are around (aspecting him). If the Moon is in Gemini say, then she cannot help him or restrain him and he has free-reign to be as destructive as he can which will harm both the house the Moon rules and the Moon herself.
A benefic would be a different story. Due to their natures, it takes a lot for them to harm the native. At worst, we can expect unfulfilled hopes and thwarted actions, at best we can see a reduced level of their goodness. Of course, Jupiter can still bring "bad" things (if he rules the death for instance) but he will bring them in a Jupiterean way and they will be "bad" for the native's life, not inherently bad in themselves.
We can do the same thing for the other two dignities aswell, domicile and bound. I don't actually see much wrong with being in detriment but I'm not in a great number of people's company there. I see it more like being totally reliant on someone else for the basics of life. This can be uncomfortable and can make you do things you wouldn't normally but if you have a good host it won't matter so much, if you're saddled with a tyrant then it is hell-on-Earth. Consequently, it may have occurred to some that a malefic in its own house should be able to do more harm rather than less since in their own house, they can act more closely to their inherent natures (it certainly did to Bernadette Brady). I find this to be based upon a misunderstanding of what being in domicile means. For me, it shows somwone in charge of their household. If you have a bad man in charge of a household, his own inherent nature (his maleficence) is, again, restrained, since he is bogged down in the duty of running his house; he is there and living it. He doesn't have time to be destructive since he is running his house 24/7. It is only when he is sitting twiddling his thumbs in Mr. Jupiter's house in the height of day that a fire-decorated wall looks ever more appealing. We want to restrain malefics since they rule things which are not conducive to life and prosperity in it. We want them occupied in their duties, so that they can do less harm. This is completely contrary to benefics, so we first must understand the nature of the planets and then the dignities before we put them together.
As for the sportsmen, I wouldn't think Mars being in Cancer would help or hinder them in any way since the dignity shows us how Mars will behave and to what ends (along with sect), not how good the native is at Martian things (I'd say sport is more Mars with Mercury anyway).
