I've looked over literally every menu based setting, I understand most of them and don't expect that wrongly-focused keyboard input would have altered the Key Bindings by mistake. As far as I can tell none of the Key Bindings look off, or even seem to mention use of the alt key.

I've tested other KDE / Plasma windows, restarted my computer, I've even tried deleting what Konsole configuration files I could find (an exhaustive list of files to purge or other method of performing a /full/ preferences reset to defaults would be useful).

I've set the problem aside and come back to it repeatedly over the course of 3 days and have exhausted everything I can think of.

What might be causing @s to be added to the terminal as if it were entered text when I press something like alt+a or alt+# (a number)?

Is there some proper way for me to absolutely reset ALL configuration values associated with Konsole?

Is there a list of all configuration files that could affect Konsole that I can examine to try and figure out what the got changed so that I can then figure out how to fix the real setting?