It seems that any use of "less than" symbol (aka html tag opening symbol) unconditionally truncate the response text without any warning or recourse (the following input is gone from editing screen as well).
I believe this to be (relatively?) recent change, although cannot be certain about that to any degree.
Chrome on Android (doubt that may matter in this case though).
To illustrate, including editing the same post this had happened to less that five times yet, or in numeric representation