I've always considered part of my skill set as an INFJ is to be able to communicate by focusing on the core of the communication and not requiring a specific style and presentation of delivery. Because of this I have tended to have easy interactions with people who many consider too blunt or direct. If it is reasonable to assume a benign intent based on the history of the person's actions, then it is almost impossible to offend me. If there is deception and malice demonstrated, then the blazing compliments feel like insults.
INFJs do value honesty and so this can reasonably take precedence over style.
Yes, this is similar to how I operate in a professional setting. I do take into account other peoples' natural dispositions/temperaments, and tend to see where they're coming from based on that - and thus don't get offended or hurt based on their manner of communication. As you say, it has to do with the intent behind the message.
In my previous job I worked with a very blunt older female INTJ with very unrefined (haha ;-) interpersonal skills (many INTJ's aren't like this, but she was more of an extreme example..part of it may be a generational thing though), and she really rubbed most people the wrong way, and due to her inability to soften/tailor her message to the audience at hand she ultimately failed to earn respect of most people, and most people simply got tired of her Te-rants. A shame, really...very bright, I typically agreed with the core of her messages but would inwardly cringe at the delivery itself, at times, as I would watch everyone else in the room zone out as she went on her cynical spiels.... but anyway. We got along well, and I wasn't scared/intimidated by her like most were - but then I could read her well enough to know that I just needed to push back - and I know she respected that I did that..possibly because so few people actually did. Most people found her style incredibly abrasive bordering on irritating, though - consequently they'd learn to ignore her over time.
For her/ other INTJ's, I think just working on softening her delivery and communication would work wonders -- think diplomacy, not strictly the message itself. You want the recipient of the message to respond favorably to your request/question/whatever. And I know our boss must have coached her at times, because you could tell when she really put forth the effort to 'soften' things and would try to tie in the other persons' point of view (rather than just her own...she had a harder time admitting to other peoples' perspectives), and she would be received much more favorably by coworkers....vs. her more natural tendencies.
As for the OP.... I can kind of relate to what others have mentioned of 'testing' people, and seeing their true character, and letting myself be 'used', possibly, at least once. Can't think of a specific scenario, and as others have said might not even be fully conscious, but yeah... just as a way to get a sense of the other person and the way THEY choose to play the game. ;-) Gives one a lot of data to work with. But I can pretty easily put my foot down if things become more of a pattern - and I'll stand up for myself or push back. So I might be perceived as uber-nice initially, as I really do want to play fair and honest and treat each other as equals, and treat each other respectfully, but IF people take advantage of that, they'll end up being 'out' and I just won't let them do that anymore.