Does Cloudsfer support files and folder names with invalid characters?

Yes. Cloudsfer addresses invalid characters compatibility. 
Cloud Providers Supported by Cloudsfer have different guidelines regarding invalid characters. Migrating files and folders containing invalid characters are fixed automatically based on the destination you have chosen:

Invalid character which is not supported on target will be replaced with the character "-". For example, files and folders containing the characters below are incompatible with Dropbox:

• < (less than)
• > (greater than)
• : (colon)
• " (double quote)
• | (vertical bar or pipe)
• ? (question mark)
• * (asterisk)

Files and folders migrated to Dropbox or any other destination will be changed to prevent errors and data loss.