As others have noted, Reb Moshe is matir trimming and even shaving. He says that kimat all the gedolim before the time of the Arizal would trim beards. The Shulchan Oruch in 181 as was also noted by others says it is only those who follow the Ari that are noheg not to trim, and that there is no reason why one must adopt this chumra.
A sefer recently came out with a title like Beards: Halchic Imperative or Kabbalistic Stringency. What I found confusing was that while clearly it is Kabbalistic, as the Shulchan Oruch says, the book seemed to be trying to make a case that we are obligated to follow this chumra, i.e., that it is halachic.
One final question I have is that there is a well-known Mishna that says Eilu Megalchin Bmoed, etc. (Gives exceptions for those who may shave on Chol Hamoed, such as those who were released from captivity, and could not shave before Yontof.) The gemara says the reason for the general issur of shaving on Chol Hamoed is that one should not enter Yontof while he is a menuval (unkempt).
Doesn’t that clearly indicate that A) there is no issur the rest of the year, and B) that it is actually preferable to shave or trim, as it is disgusting to walk around otherwise, especially on Yontof.
Similarly, the fact that an avel Rachman Litzlan is forbidden to shave, doesn’t that indicate that the rest of the klal is allowed?
How is kabbala allowed to contradict an open and shut gemara? We go like the gemara.