Yeah it often depends on the kinda browser one is using as there some mobile browser like the Chrome browser, Opera browser and some others that when you accidentally use the backward keys while still typing but if you use the forward keys it will display what you're typing again so it basically depends on your browser.
In a case of poor network or maybe your network becomes unavailable while typing, it is advisable to copy what you are typing before refreshing the page otherwise you will lose the whole content of what you're typing, and in a case whereby you are done typing and you hit the post button and the network goes of what you need do is keep refreshing the page rather than using the backward key as you may also lose the whole content of what you typed.