I have read these comments often now and it's just something people make up to justify not being able to buy masks.

Which part of this is being made up? That improperly fitted mask isn't protective? That unless you very carefully handle a mask when taking it off, you'll transfer the contaminants from it onto your hands and/or face? That people compensate for risk[0]? That those masks are disposable and lose their protective power over short time (hours)?

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[0] - https://en.wikipedia.org/wiki/Risk_compensation

Yes. Do you have a study that shows that a mask that has not been fit tested either provides no protection or actually increases the overall risk to the wearer?

I have looked at a fair bit of research on masks lately, and everything I've seen is that they are significantly protective, and, for example, reduce your risk of catching SARS by about 70%.

Yes, if a mask doesn't fit properly, some air will come through the sides. Even in that case though, the mask is still filtering some air, and it's protecting you from touching your mouth or nose, and it's protecting you from droplets hitting your mouth or nose from being coughed or sneezed on.