Passage is an artifact subtype that grants the following abilities:

> When this enters the battlefield, if the gate is neither open nor closed, close the gate.

> : If the gate is closed, open it. Otherwise, close it. Activate only as a sorcery.

Your reminder text and comment contradict each other.

The comment uses the wording of a triggered ability ("When") and an activated ability (":"). Reminder text has certain freedoms, but must always correctly reflect the kind of ability it represents.

The current wording of the reminder text are more a game fact and a special action (compare suspend, foretell, morph, rolling the planar die) i. e. neither of these can be interacted with with Stifle.

For the record: I think, the reminder text is/should be correct. You don't want these to be triggered/activated abilities, but in that case you shouldn't use triggered/activated ability wording to describe them in comments or the details page.

I'm not a fan of tying the rules of tracking gates to the subtype. I'd suggest also changing the reminder text to

If the gate has never opened, it is closed.

or

The gate starts the game closed.

More specific to this particular card: You probably want the text to be "one or more Spirits enter the battlefield" etc.

I suspect that the special action to interact with the gate purely b paying mana will lead to some bad gameplay/balance issues

I based adding the gate to the game on day/night, but I guess that changes even when you don't play daybound/nightbound cards. It's probably fine to start the game with the gate closed, and just be careful not to make cards like Feed the Stoma that don't open the gate and then have an effect with a closed gate.

I definitely don't want the passage ability to be a special action. I was going to make it like food or blood, where every card with the subtype had the activated ability written out, but then there wasn't room on the cards for other abilities. (Since it makes sense that you can't open the gate if it's already open, but you'd need to spell it out like The Celestus.)

I suggest keeping the reminder text "(The gate starts the game closed.)" on all common and uncommon cards. The activated ability seems like a good default place for it, though any ability that references the state of the gate would suffice.

Speaking of Feed the Stoma; that's an instant, so someone might cast it in response to your activation to force you to re-open a gate that you may have wanted to close. Maybe updated Twiddle wording? "You may open or close the gate. Activate only as a sorcery."

I explained why I wanted the wordy template, but that's less important if the gate starts closed. Plus it should be obvious you can't open a gate if it's already open. Making the passage ability optional makes sense for the reason you said

Btw, on Kamigawa the name <foo> Shrine hopefully is used on a Shrine enchantment card.