MagnuM Well, after taking my Switch to a friends house (also an old LCD Samsung Series 6 but Plasma instead of LCD) and having the exact same issues occur, I was starting to doubt my Switch more and more. I hate doing this, as the store likely has to swallow the loss, but I asked the manager at Shopper Drug Mart if I could do an exchange, even though they mentioned that wasn't their typical policy and that they usually ask customers to go through the manufacturer (i.e. Nintendo). Doing so would mean not having my system during the holidays and my week off, but I guess my niceness paid off, as she made an exception for me and allowed me to have a system exchange performed.
I hooked up Switch #2 in the exact same way as Switch #1, and there are no more flickering lines anymore. Looks like I may have just had some bad luck and was handed a slightly defective system.
There's another more unfortunate possibility for Switch #1 that I'm hoping is a non-factor! I was setting it up in my basement that has a cushy high pile carpet that generates a heck of a lot of static electricity. Each time you shuffle around on it, either on your knees or your socks, you become ... ElectroMan (or Woman!). Every time I touched the Switch handheld while setting up the original system I would give it a shock that would always startle me like it does when you touch a lightswitch. I'm hoping these repeated shocks (it must have gotten at least 10) didn't do anything to the system. This was always against the handheld instead of the dock, but the areas I was shocking it at was always along the bottom edge near the charging port. Could the flickering lines of my first Switch have been caused by static damage perhaps?