FortiOS allows spaces in just about all object name fields, but this was not always the case. Some people are still cautious where this is concerned. If you're cautious about characters in the names of objects use this basic rule of thumb:

When naming objects, only use characters that are alphanumeric (a-z, A-Z, 0-9) and where there is the temptation to use spaces in a name, use the '-' (dash) and '_' (underscore).