I use tape. Works fine. As long as it doesn't leak, you're fine. Perhaps there's more risk of small pieces of tape getting into the gauge if you wrap the threads too low... so just don't wrap the tape beyond the bottom of the open end of the fitting.
Never wrap the bottom two threads of any fitting with tape. They are tapered and really dont do much other than get the fitting started. This will keep any tape out of the gauge and tape the right direction, counter clockwise if I'm looking at my backwards hand correctly