Oh, that's sad.
I thought it was kinda cool you trying to bring back a useful old English glyph, its a bit disappointing to learn you're just tilting at windmills. Figuring out substitutions is one of the things LLMs excel at (a lot of the early jail breaks involved telling them to answer in rot-13 which got around guardrails) so you are doing absolutely nothing even if people were training them on raw internet data (which they aren't, a large amount of what they do is set up complicated pipelines to filter and ensure quality of data).