I use <> to specify people, e.g. <bob>, and  to specify customers, e.g. [acme]. However these don't work.
indeed, some special characters cannot be used within labels. Thank you for pointing it out, I will forward this to the developers and will notify you if it can be fixed.
For now, as a workaround you can either use the following characters within labels which should work properly:
or use a specific color for labels referring to people or customers (this can be set when viewing all labels through the gear icon menu).
unfortunately, these characters <>  won't be supported at this point, but we may include them in future development.