Chayei Sarah, my first Shabbat in Berkeley, California - I had what in retrospect was a poignantly amusing case of shock when realizing that I was davening in a "Modern Orthodox" shul for the first time in my life.
So there was, in my jet lagged, childishly bewildered and fish-eye lens opinion, "no mechitza" in this Shul, which otherwise conducted itself just like any other Orthodox shul I've ever davened at in terms of the liturgy and service.
I said (in a kind of almost stammering, disconnected way) to several people afterwards how disconcerting that was for me that there was "no metchitza," and I kept being told by perfectly nice, kosher, normal and not crazy people that there was indeed "a mechitza."
Finally came to the understanding that a "mechitza" is not necessarily understood the way I understand it or have experienced it, and that might be one of the manifestations of the word "modern" in "Modern Orthodox."
I felt extremely tense which wasn't because I was in a new place, alone, and didn't know anybody. Usually that's a fun and exciting activity for someone who is hyper-social, curious and friendly such as myself. The tension was because everything about the service was "normal" except that I felt naked. I was too disoriented to figure out a fix and just kept trying to talk myself down (which didn't really work).
Discussing it afterwards with various people reminded me that there are a variety of options and fixes to be applied to make me more comfortable, and I can deal with it next time.
I wouldn't have experienced this tension at all if I had gone to a Reform or Conservative or Renewal shul, because I would have expected and have calibrated my Neshama, so to speak, for the reality of davening in a community without either a mechitza or separate seating for men and women. It was the word "Orthodox" that threw me off, my assumption about what that meant in the phrase "Modern Orthodox" was not accurate (probably because I have never experienced it before).
I realized more than ever how important the feeling of private, sacred feminine space is to me while davening. I've never experienced the mechitza as a way to keep my feminine energy from "infecting" (as someone I know has said) the masculine energy on their side of the mechitza. 100% and from the first time I ever davened behind a mechitza I experienced it as a safe, sacred space of feminine spiritual energy and was grateful such a thing existed. I do love to join my relatives and friends at their shuls, often without a mechitza, but as I said before I calibrate my expectations and Neshama to that environment and it's always for a special occasion, not for my "regular" davening experience.
I can be inclusive and welcoming and non-judgemental better than anyone in the world - but I still know what I like! I like privacy!!!