I was not rude at all, I tried to explain you that charger and those strange letters cannot have anything in common, it must be a coincidence. One explanation is that it is set to another language and you do not know that (did not insinuate anything, because it is not relevant whether it is yours or your friend’s or some else’s etc.).
If, after reinstalling the system, it was OK, but later on turned bad again, then noondaywitch may have given the right hint.
Another possibility, also physical, is that battery may have swollen up, and presses the physical keyboard. This reportedly occurs from time to time. The test may be simple. Shut down the computer, and remove battery, wait for some time, and connect charger; then power on. Using a MB without battery is not of course recommended, but for testing purposes for some time cannot hurt too much.
If a system issue, as Apple engineering suggested, and reinstalling over the older system, without erase-and-install, is a total nonsense, because you do not remove the corrupt files, you put new ones over the old, ill ones. If you want to test this thread, i.e. software issue, then backup your data and make a clean installation via erase-and-install, i.e. erasing disk first, so that you have a virgin new system.