I have noticed it only works as a startup command line parameters rather than bitcoin.conf
Discussion
Ah. Do you really need it? Looks like it's for nodes to communicate to one another so it seems crucial
Your node can't contribute to the network unless you expose this port and poke a hole in your firewall (unless you use TOR). If you don't do this then you are just a consumer. It depends on your intent. It's also more secure to have more nodes connected to you. For example, if you are limited to 8 connections and all 8 are bad actors, then you could run into problems (however this is quite rare)