Does House/Placement affect the Planet?
This is a very good question. If i understand Ernst correctly, planets are planets - producers. They produce the things that they are assigned to produce in life. They are not good or bad per se. But now you put the planets in different houses/bhavas, then they manifest differently and you will get the effects of the things that are being produced in those houses/bhavas. Things could be smoothy or easily manifested or manifested with hardship and difficulty depending on the houses that the planets are in. If that is the case, the house placement definitely affects the planets and not the planets affecting the houses because planets produce no matter what house they are in. How well the planet manifests depends on its house location, and the planet's relationship to that house such as dignity. Planets do well in certain houses and not so well in other houses. But it is the houses that control the quality of the manifestation of the planets.
At least that is how i see it. If i am wrong pls let me know...
Depending on its location as counted from the lagna, it can more readily or with more difficulty produce that which it is and that which it rules.
Why, though? A planet exists before the houses and the lagna even come into being- why should it struggle to produce "that which it is" based on the house, wouldn't that be more based on the Avastha? I understand the latter i.e the bhava it rules will be a struggle (or not), because that doesn't even exist without the context of the lagna.
This has to do with Dig Bala, one of the (most important) Shad Bala strengths.
For example, Mars has full dig bala in the 10th house, if Mars is in the 4th, even if it's in own sign, it will not produce Mars things in a very significant way. It's so important to look at dig bala of planets.
Then, dushtana houses are just "bad" places, any planet is going to have a harder time developing if it's in a "bad" place than if it's in a more gentle place. That tough placement has its reasons, of course, and 6/8/12 are necessary and useful, but they're just more stressful placements, that are gonna cause the delay, destruction or loss of something that planet rules, at some point; in this case the dignity is important and a strong planet will not succumb as easily to that stress as a weak planet.
hope this helps