Grammar is important and more so in some situations than others because proper communication is vital. Unless someone asks for assistance, then help them with what they are asking so that they can learn and get the correction(s) that they need. Especially with being an ESL and learning assistance teacher at one point, there is no way to know where someone is coming from in their background, capabilities, or desire to achieve in that moment. However now when I do see mistakes including my own, unless asked for help or in asking for help, it is not my place to do anything other than to live and let be. Then there is that mistakes also just happen, just forgive.