rraypo

All absolutely true! Well stated

Not sure what this refers to.  The only "right" when it comes to US immigration is the right for the USC/LPR to petition an eligible family member or fiance.  That's it.
 
Being the spouse/fiance of a USC does not in and of itself confer any immigration benefit.

Exactly.  And if it was a reason,  it would be hugely unfair for any couple who cannot or choose not to have children together.

I'm really not sure why people think pregnancy is reason for expedite. The (obvious) counter-argument is that the couples could have simply waited to get pregnant until after the immigration process is over and both people are inside the US together. 

the baby is just a baby and mother is breast feeding
no medical condition was ever mentioned 
OP thinks bringing the baby to the US will show the need for the mother to come with the baby 
 
Sorry OP ,  but your wife needs to go thru the same long drawn out process same as the rest of us

You can thank those from her country who have perpetuated fraud for the additional scrutiny.
 
And the global situation  with Covid is obviously out of the US embassy’s control.   
 
For  others in this situation (pre-interview), I would definitely recommend not going for 18 months without a visit, to a third country if need be.

After waiting since April due to covid, my fiance finally had her interview today and was rejected. We have met 5 times prior to covid and haven't been able to be together for over 1.5 years due to covid. The interviewer said they did not have time to look over the paperwork, and in the same breath told my fiance that she didn't bring enough evidence to support our case that we have a "bona fide relationship". It's very very unclear to me how we can provide more evidence supporting our relationship when the time wasn't taken to review the material that we brought in the first place. How can we have any chance to win on this?  They asked her if I was present (which clearly I was not) and it's not possible to go to Vietnam currently because they're still closed from covid. That seems like a really stupid question to even ask her since they've been closed since March 2020. 

They are not required to consider additional evidence brought to the interview.  That is why, for high fraud consulates, "front-loading" petitions is considered critical.
 
The inability to visit each other due to COVID is not something they would take into consideration.  They would say that you could have visited each other in a third country.
 
At this point, I would say you're better off just trying to marry in a third country and filing for a spousal visa.
 
I'll tag a senior VJ member who has a lot of firsthand knowledge about the HCMC consulate:  @aaron2020
 
Best of luck.

Since the entire K-1 visa eligibility rests on both parties being legally able and willing to marry, certified copies of divorce decrees and updated statements of intent to marry should always be brought to visa interviews.

Yes not having the original divorce certificate is dangerous.  We had it for the K-1 interview and were not asked for it.  We had it at the I-485 interview and were asked.  

US Citizens are required to enter using their US Passport.

I personally know two people who have had home visits by USCIS investigators. One was here in Oregon where the Chinese beneficiary was already living in the USA, the other, was in Brazil.  In both cases, they were very simple and short visits, and in both cases the investigator wanted to look in the closet of the person to verify they actually had suitable clothing and sere in fact living there.