Big fat NO to the first question. I feel that with the increased availability of rare items that would otherwise stay in a studio, flipping gear is partly responsible for continued demand, and if everyone who does this sells for profit with that kind of demand, prices can only increase. This is even true for the person who sold said item and later regretted doing so, and now wants possession of another one.
Interesting point but I do not think the demand is driven by the selling of gear - rather the selling of gear is driven by the demand.
The demand side of the equation is what determines whether something gets sold. If somebody found 3,000 Minimoogs in a wharehouse and put them up for sale this would not increase the demand for the Minimoog but it would would it cause the price to go down a bit.
People want the Minimoog because it's a good synth - not just because it's being sold.
The demand is what makes the prices go up. More people selling gear increases the supply and actually drives the prices down.
Having said all that, I agree that you should buy what you want and use what you have.
There wil always be something you can't have but you should not focus on that. Focus on the setup you have. If you do have to buy, be flexible and wait for a killer deal. That way, if you decide to sell it later you won't have to take a loss.