Please give me as much information as possible off the top of your head about what specific cameras you encountered that had left-handed thread screws in them. If it helps I need a warning for the following makes and models:
ZI Contaflex II, Contessa 35
Voigtlander Prominent, Vitessa L, Bessamatic
Agfa Solinette, Karat
Pentacon FB, Exakta Varex IIb
Kodak Retinas (I, II, III), Signet 35
Balda Baldina (non-folding)
I have a few more (but not many more, much less than I've listed: I'm a modest camera owner) but those above are the first ones that come on my mind.
If you can think of anything beyond my list - please go ahead and name it if it fits the subject of the thread!
I once managed to break two LH threaded screws in a row on 2 identical cameras. Those were holding the film counter dials. On the first one I though: What a stubborn screw! - and applied a little more force when unscrewing it - Snap!
On the second camera I thought: OK, on the first one it must've been frozen. Now this one should surrender! - Snap!
Those were 2 cheap FED 5B's and later I used them for spares but I wouldn't like to break a LH threaded screw in some expensive camera like Voigtlander Prominent, for instance.