When a user creates a folder containing (\) or (/) for example, he/she is not warned that this is not authorized, same if total folder length is too long, ... . The system allows it to be created and thus can generate a lot of issues. I have a user here with over a thousand (yes, I know...) folders, 400 of them contain a (/). This is now causing trouble on his Android device. Telling the user he should not used those chars, gives an answer like "well, Notes didn't warn/prevent me not to ...". Renaming them is impossible if you don't have an in-house dev.
IBM references on the limitations :
The name is case-sensitive and can be any combination of characters, including letters, numbers, spaces, and punctuation.
The maximum number of characters a view or folder can have is 64.
The total number of characters from a parent view or folder to its farthest descendent child cannot be greater than 130 characters.
The use of a slash (/) or a backslash (\) in a folder name can cause unpredictable results within a database. For example, the use of these two characters is known to cause view problems as well as problems with the unread marks count for folders.