This is an advanced board (as opposed to crisis which is more raw emotion), so let's take this on at a high level.
Forget BPD for a minute. Let's consider any mostly healthy relationship.
Is it beneficial to interpret what our partner is communicating? Or should we take them literally and adopt a life philosophy that if they can't express themselves, that's on them.An emotionally intelligent male reads his partner (and true for the other sex, but this was asked in a male context) and takes it on himself to understand people in the context his entire experience with them.
If my new date tells me, for the first time, that she loves me - and then at dinner later that night, she tells a casual friend she loves them, she loves calamari, she loves the Dallas Cowboys, she loves Meryl Streep, she loves her boss, and she loves old Jim Nabor's albums - you can bet that I'm going to wait for more context on the "I love you" statement before I buy her a house.

This is reading people. People often say things in ways that can not be taken literally. There are also times when we need to take what is said very literally. Knowing when is emotional intelligence.
Some people read others well... .some are complete bumbles... .its a skill and invaluable.
OK. For someone with BPD traits - highly emotional, prone to overstatement (both positive and negative), very defensive... .1) I don't see how anyone could ever feel confident in knowing anyone else's mindset, especially that of a BPD.
Reading someone has this risk, for sure. It's hard and its an ongoing process to learn to read someone and we need to be careful not to get over our skis.
2) This seems to be the crux of this idea of being in a one-way relationship, where the non fills in the blanks on behalf of their absent (emotionally, physically) BPD. "Oh, he's just afraid of the intimacy." being an example of such a generous interpretation of their supposedly true intent or actions.
This might discribe the difference between reading someone and misreading them or expecting them to be understood according to some "BPD script".
3) It can also short circuit the demands of a bigger conversation/discussion that needs to be had between the non and BPD. Such a convo could start off: "What did you mean by what you said when you said, 'XXXXXXX?'"
Absolutely. Reading someone includes asking this type of question at times when such a statement isn't inflammatory or the person speaking in emotional overdrive.
Good discussion!