Quote: Because M42 lenses are cheeper, plentiful and can take photos of comperable and sometimes better quality than K mount lenses. It can be quite satisfying modifying them and with care some conversions can be made completely reversibly.
as much as I love Takumars, this statement is completely false in my opinion. the origional K series of lenses were as far as I know directly based on their last Takumar counterparts. so why would there be any difference in IQ? in fact there are plenty of Kmount lenses that are supposed to be much better in optical ability than the earlier Takumars. as for being cheaper, again I disagree. K, M and even some A lenses can be had for much cheaper than Takumars. for 3rd party M42 lenses I would agree. also you have a number of option in focal length that have been made available in Kmount that never was in M42. as for the modification. yes I agree, there are a number of mods you can do that are reversible. but the most common method of carving a notch in the base to use the Kmount lock pin is obviously not reversible and as I said earlier isn't even possible on most Takumars.
I don't have a problem with people doing whatever to their lenses (though I don't like destructive, even just cosmetic) but I think that between the K and M series you not only have all the options available in M42, you also have options not available in m42 and you don't have to worry about using adapters and modding lenses. and you get equal or better IQ. so if you are not keen on using the adapter and dealing with a screwmount lens, I fail to see the point in having them. its bet to have either all screwmount or all kmount. or have a body dedicated to screwmount. that's what I did. its cheaper and easier in the long run.