Welcome to the forum mujzeptu. I am also a left handed shooter, and just took delivery of my 15-22 last week. I also read those posts related to out of battery (OOB) firing malfunctions, and came away with these conclusions.
1) Yes, it did happen, but it appears to happen only on early model 15-22's.
2) Regardless of what your dominant shooting side is, don't hold the gun by the magazine.
3) If I buy a new gun, the chances of having this problem are extremely small.
4) If I were to buy a used gun, the first thing I would do is send it back to S&W for service and upgrade to address the potential for the OOB condition on an older gun.
I do not hesitate to shoot my 15-22 left handed, and put at least 300 rounds through it weekly. Matter of fact, I'm off to the range in a couple hours and have 400 rounds for the 15-22 and another 200 rounds for the SR9.
I would recommend you buy it, but buy a new one with a serial number that begins with DUU.
John