Hi Chloe,
I like your post. I agree with what you think on the pros and cons of public communications. It is great to have opportunities to discuss and share thoughts with mindful peers. Inappropriate comments will indeed alienate people from others. In addition, arguing on the internet is inevitable. Therefore, when I think about the downside of public online discussion, I usually focus more on viral violence.
I also have a similar idea to you on digital identities. Digital identities help the big data to match people with a group having similar thoughts. It also helps organizations target customers. Thus, just like what you said, the data is precious and beneficial to the personal learning industries.