I disagree that saying something in response is a good idea simply because he's texting "hi, how are you" likely to pull her into a conversation again. she has done well not to respond and I think he knows already that it's uninvited at this point due to that. You owe him no explanation as you're exes and considering the context that you've been just ignoring his texts and you dont' ask any questions regarding ties due to other circumstances that there are none. Outright blocking is likely still the best method.