Experimented with various ways to update the notif body text on comment update

As usual, something I thought was simple became quite difficult. And Pareto's a bitch - the last 20% takes 80% of the time, for sure!

I can update notifs upon updating a comment in 3 ways:

* regex - elegant but might not capture edge cases, and without testing, lots of uncertainty
* plain Javascript functions like split(), splice(), join(), push() - convoluted chaining of functions together, but readable
* create a new content field in notifications content type, to hold just the comment text - simplest, but have to refactor widely.