This sutra is closely related to 2.33 and continues the train of thought. I love the idea of pratipaksa bhavanam or having opposite thoughts to prevent the thoughts that cause pain.
Iyengar: Uncertain knowledge giving rise to violence whether done directly or indirectly or condoned, is caused by greed, anger, or delusion in the mild, moderate, or intense degree. It results in endless pain and ignorance. Through introspection comes the end of pain and ignorance.
Iyengar comments that pain comes of three types, over indulgence in pleasure, non-deliberate habits, and genetic or hereditary causes. Only through discrimination, that dubious knowledge, vitarka, is curtailed.
Bryant: Negative thoughts are violence, etc. They may be [personally] performed, performed on ones behalf by another, or authorized by oneself; they may be triggered by greed, anger, or delusion; and they may be slight, moderate, or extreme in intensity. One should cultivate counteracting thoughts, namely, that the end results [of negative thoughts] are ongoing suffering and ignorance.
Bryant comments on the various ways violence can be done. For example, killing an animal oneself is first category, purchasing the meat that has been killed by someone else is the second type, and allowing meat consumption to occur in ones sphere of influence, even if you don’t consume it, is the third type. This was a revelation to me as I grew up with the ten commandments and only considered the first type.
Taimni: As improper thoughts, emotions (and actions) such as those of violence, etc. whether they are done (indulged in), caused to be done or abetted, whether caused by greed, anger, or delusion, whether present in mild, medium, or intense degree, result in endless pain and ignorance; so there is the necessity of pondering over opposites.
Taimni points out many of the same points as the other commentators but also says that the yamas and niyamas cannot be practiced separately as they are all tightly interwoven. He says that this sutra describes the factors to transform undesirable tendencies into desired tendencies. How many self help books days could be condensed by meditating on this one sutra ;-).
Carerra: When negative thoughts or acts such as violence and so on are caused to be done, or even approved of, whether incited by greed, anger, or infatuation, whether indulged in with mild, medium or extreme intensity, they are based on ignorance and bring certain pain. Reflecting thus is also pratipaksha bavanam.
Carerra says that yoga provides two ways to counter negative thoughts. Suppression is not one of them as the thought will most likely return. Bringing attention to an opposite thought, for example reflecting on peace when anger emerges is one technique. The second techniques is for after the negativity passes – use self study and self reflection to understand the root of the negativity and try to burn the seed that started it.