While I had not experienced quite the same scenarios as others on this thread, my problem appears to be very much related.
I always let pages fully load before interacting with them because Chrome OFTEN crashes when doing so. So that hasn't been a problem elsewhere, and is also not a solution for me.
That problem aside, my main issue is with using Facebook through the Chrome browser. The FB app blows, by comparison... which is why I prefer to use a browser. But with FB, it is constantly refreshing and reloading SOMEthing, right? So no matter how long I wait, no matter how short my typing/response, the keyboard invariably disappears mid-type. Happens so much I had to come find a thread and possible solution for it. By comparison, it has yet to happen once in this entire comment here.
Matter of fact, I don't recall it happening ANYWHERE but on FB. But there, it's nearly constant.
The main difference in my situation is that since FB on iOS often requires a tap to "select/highlight" something, then a second tap to actually execute the action, luckily the errant tap upon keyboard dismissal doesn't select a link or anything. Although, now as I think about it, that HA happened to me before. But I do still have to re-tap the text/comment box to continue with text input.
Also, there are times when the text input lags considerably. Often I just keep tapping away, and it will catch up... sometimes with a flurry of keystrokes. But obviously that delay often creates misspellings and incorrect input. So the need to backspace or select/edit is required. This last issue feels like when a computer is low on RAM or something, and is sort of staggering with its performance. But that's just an observation/opinion/guess.
I'm on an iPad 2, iOS 6.1, and almost exclusively use Chrome, so my entire problem is in Chrome, while on Facebook.
PLEASE someone tell me this problem is being addressed! >.<