I'm not familiar with how difficult it may be, so please tell me if I'm off base. But couldn't you offer the option for either text logs or HTML logs? I know that when given the option, I opt for HTML logs for the ease of reading.
While I haven't implemented the logging yet, I'm thinking about storing them in the JSON-format. Messages are already stored as JavaScript object, so I think this is my best option. And exporting them as .txt on demand, shouldn't be a problem either.
Thank you for the feedback