Not sure what lists you're talking about, but it's nerding time anyway.

The backslash (the \ symbol) is used to "escape" characters in the software world, i.e. tell the software to treat the following character as a simple symbol, not some instruction. It's very well-known among developers, so if they happen to be the ones writing guides on Markdown (the syntax where you use asterisks and some other symbols to dictate the final layout while having the luxury of being able to edit the document in a plain-text editor), it can actually elude them because it's mundane.

In fact, some software won't allow you to use the backslash in short text fields such as names or passwords because doing so could potentially open up security risks where the malicious actors "inject" some instructions into software to cause all sorts of trouble. On the other hand, this is probably a redundant old measure, as there are usually other means to prevent this kind of attack today, but that's the power of habit, I guess; and, well, if it's a simple measure that works, there's not much reason to get rid of it, is there?