I have Neptune in the first house, though not conjunct the ascendant.
Here is my personal take on the question.
The best way I can describe a challenging aspect to Neptune is that it tends to "dissolve" or "erase" what it touches. Now you see it, now you don't. A Neptune trine tends to give a rich imaginative life.
The trouble with Neptune conjunct the Asc or in the 1st house is that what Neptune tends to erase is one's outer personality and consequently, one's sense of self, because the first house suggests how other people will respond to us. Consequently first house Neptune people can be on a long-term identity quest, which is ultimately futile, because Neptune will keep erasing whatever firm sense of identity the person thinks she's captured.
Here's the kicker. With Neptune in the first or conjunct the Asc from the 12th, the person can become quite the chameleon. If you don't quite know who you are, there is a tendency to try to become the kind of person other people seem to want you to be. You learn to be nice to people if you think that's what they want. You might side with a political view you don't actually support, because that is what someone else seems to expect of you. Sure, you can be a raging Scorpio or an eccentric Aquarian on the inside, but why expose that to people who will only misunderstand you?
Well, this gets tremendously wearing and tiring on the natives; notably if who they are for themselves is very different than their first house placements. Consequently, privacy is a good option. Just opt out, so you can recharge your batteries. So is just not sharing very much about one's inner life.
I would suggest looking at the person's moon, as well. If the moon looks pretty strong and robust, you probably won't see such a strong shift. If the moon is afflicted or is in one of the signs that needs approval, the Neptunian will do a lot to avoid having his feelings hurt.
A classic Neptune in the first house person was Marilyn Monroe. It is a good placement for actors because the natives know how to slide in and out of role-playing. They feel just fine pretending to be someone else. Monroe also had the ability to go incognito on the street because she could "play" being someone other than her "blonde bombshell" screen personality.
The downside is that Neptunians can appear as deceitful to others. It can be difficult for others to know where the Neptunian stands. The reason is because once the Neptunian does develop a personality, Neptune starts to dissolve it.
Of course you have to look at the whole chart! Zonark doesn't strike me as fitting my picture, but then we've never met.