How important is it for the channeler to understand, in a deep sense, the subject matter pertaining to the question that is asked?

This can be all-important in some circumstances. If there is a question asked in total ignorance, there may be but the vaguest response, and may be a major disappointment for the original party wanting the enlightenment. This scenario of a profound ignorance prevailing on the part of the channeler is much akin to the situation where a question might be asked in a foreign language and then the channeler expected to convey it and receive an answer in exchange. This is not impossible, but does put constraints on things and will matter greatly about how the exchange proceeds. If there is additional stress and fear on the part of the channeler that they might fail and let down the questioner, this can get in the way. It certainly adds extra requirements and raises the bar to ask the utmost of the divine realm to skip over the channeler entirely, and provide information of direct interest and value to the questioner, and ignore the intentions of the channeler with regard to the content of the question. If the channeler, nonetheless, is keenly interested in serving, that can make up for the deficit in personal understanding to some degree, but there will be a dilution effect because even though the undertaking and its limitations are understood, and it is up to the channeler to maintain a strong desire and a strong intention for the successful receipt of a cogent, intelligible answer, and a requisite level of belief in the possibility, this raises the bar always and may or may not be successful in particular circumstances. So this introduces another variable, which is the belief quotient of the channeler, which is a critical element. A high level of belief is needed for successful channeling in the first place, particularly so of an authentic divine-level being. Low-level beings are easy because they very much want to engage with you and will see to this directly through a manipulation, and all that is required from the gullible party is a desire for a connection beyond themselves. And while they have in mind a particular divine-level target, if their belief is inadequate, an imposter will step in quickly and take the reins, and the divine realm must allow that to happen, by the rules of engagement, to honor the free will of a would-be channeler of the divine to falter and connect with a low-level being because they fall short, and then do not recognize they have taken a misstep, so the consequences will flow from there.