Beware the ego. You bring it with you into the Course, and it will do everything it can to delude you, confuse you, distract you, blind you, and make you use the Course as a weapon.
One of the main ways that it does this is by engaging the intellect. Whatever you are experiencing right now, that is your most real-seeming experience and represents your current truth/beliefs. In order to really change that experience you have to undo some ego, which will shift you to experiencing something else.
The ego doesn't like that. The ego wants to keep the ego and increase itself. A major way it does this is through shifting into concepts. In essence, attempting to take on board "truth" which is too far outside the envelope of what you actually are experiencing, it shifts awareness into the intellect. You can "conceive" of the thing being talked about, but you cannot experience it.
The intellect is the ego's attempt to bridge the gap between where you are most authentically at, and where it pretends it wants to be. It is a tool for dissection and analysis and trying to find answers in illusions. It's a mechanism for judging, it experiences reactions, and tries to make realities. It's part of the dreaming mind.
What happens unfortunately is that the intellect becomes strongly engaged by studying the Course. There are so many concepts, theories and ideas in the Course. There are so many quotes which say or thing or another. A student will amass an internal library of all these things, and then the ego will use them as weapons and justifications.
What happens is, because the intellect takes you away from the present experience and into fantasy, the intellect becomes a way for the ego to avoid the present. The intellect loves to be a quotation machine, it loves to get hung up on the form of words, it loves to fixate on what is specifically in or not in the course, and it loves to be the ultimate judge or the authority or thing which figures out and decides what is true or not.
What I've seen is, some Course students become so lost in the form of the Course's words, the theology, the quotes, the concepts, that their intellect goes into overdrive. When you try to hold a normal conversation with these people, there is practically nothing you can say which won't be picked apart. You can't speak to these people with normal words because if there is any overlap with course words or if the course seems to have a redefinition of a term, they will see the use of the word as an error.
What then happens is they will have a reaction to a perceived error, will use the course to back up "why" its an error, and then the conversation will shift away from presence and into the course concepts where they'll assert all the reasons/quotes as to why what you said was wrong. You don't even really know what it was you said, being normal, that was so erroneous, and then you end up being bombarded with all this "correction" that you didn't even need.
Another favorite ego tool is to jump around in the levels. This is a classic move. Basically you're talking about something within a given context. Maybe you're discussing the ego or the world or something. You say something. Their ego intellect kicks in and sees a opportunity to be right, or basically pulls up a quote or course concept which they believe has truth to it, and they then use it as a weapon. They'll jump out of the `level` or context you're discussing on, and jump into some super-high conceptual level of the course. This "trumps" whatever you said, and seems to render you in error, or less true, and therefore you're wrong.
For example, you could be talking about forgiveness or how to apply it to something, and you say something, they get triggered, and then they suddenly come out with something like "that doesn't exist" or "nothing happened" or something... something at a higher level, which basically ultimately is true, BUT, it's being used as a way to discredit and overly dismiss whatever you said that wasn't even a point of contention. The person positions themselves with weapons of truth, concepts, in order to have the best most high trump-cards possible, so that no matter what you try to discuss with them, they will constantly undermine you. There is no way to hold a normal conversation with such people.
I think we all do this to some extent. But Course students especially are prone to this. It is so easy to get hung up on what the Course said on some matter and to then use it as a way to be subtly right, to use it against other people, to make people wrong etc.
I recently was in a group of people discussing ACIM stuff. I was shocked. I couldn't believe how much of this intellectual prostrating was going on. It seemed practically impossible to say anything without some person jumping all over it and pulling it apart, with a sort of "I've got a better truth" attitude. Even saying things which were absolutely nothing to do with the course whatsoever, which suddenly were turned around and explained to be false or in error because of something it contained. It turns into an addiction to correcting people.
The intellect can be used by the ego to really firmly latch onto the concepts as though they are the truth. They are held onto like precious jewels. And then they are used as weapons. The concepts are not the truth itself. Truth is an experience. Getting lost in debating the Course is very easy to do. It's possible to amass a considerable body of conviction about what the Course is saying or meaning and to then be so rigid and fixed in that that you can no longer talk to people normally or allow them their mistakes.
One person I was talking to was so distracted by intellectual positions that it was almost like talking to no-one. I would say one thing, they would do an instant bypass, find some other quotation or concept to go against it, and throw it back at me. I also wrote a few posts which were clear and obviously correct. But what happens is, people will then read it, sort of quietly refuse it, find one word you said which was slightly "not pure course-correct lingo", and then go in a diatribe about how you were wrong, completely glossing over and ignoring what you actually said or whether it was true.
This is what the ego does. It creates diversions. Distractions. Cover-ups. It makes noise about something, anything, other than what is immediately present. It pulls you away from the here and now. It takes you out of conversations and into wars. It uses its prowess to launch counter-attacks to perceived attacks, which it itself put out there with its mis-perceptions and judgements, and then reacted to.
You have to beware of the ego doing this. It will try to use the Course to point out the ways that people are wrong and then react to this perception by trying to correct them, when in fact it is your own mind which is at fault. It's just another way the ego projects responsibility and blame.