Just created an account here to report this issue as well. This character replacement is probably fine for normal text, but it sadly also happens when formatting inline code with markdown.
Sorry, but I have to ask: What does “is by design” actually mean? I also work with other Markdown tools that don’t change the actual user content without asking. Because that’s a key point: In this case, it’s not just the appearance of the text that’s being altered - a character is actually being replaced with a completely different one. For power users, programmers, and IT admins, this means tons of broken code snippets. Having to always prep the text to be inserted with escape characters first is unreasonable in the long run, especially with longer code passages. Anytype should at least provide an optional setting so users can decide for themselves whether the double dashes can be replaced or not.