The double-struck L and I were removed in version 8.0.1. See here.
There was a discussion about the use of double-struck characters and alternatives to them since they’re not so easy to type but it came to nothing. That is readable somewhere in the forum but I can’t find it right now and anyway it’s not relevant anymore.
So, the answer to your question is to put local/instance in front of your variables: it’s not case-sensitive and you can use underscores too if you want - like local_variable.
Hope that helps.