Possible to change Messages up/down key behaviour?

In most single-line text edit fields, pressing ↑ moves the cursor to the start of the line, and pressing ↓ moves the cursor to the end. But in the Messages app, the behaviour is slightly different; it seems to consider 3 positions: the start of the line, something like the last location of the cursor, and the end of the line, and pressing ↑ / ↓ cycles through these (so e.g. pressing ↑ then ↓ returns the cursor to the same position). I can see some logic to this for people who press ↑ or ↓ accidentally and want a quick way back to their old place, but I find it jarring since I'm used to the standard home/end behaviour. Is there a way to configure it? I'm not sure if this is Messages-specific, or something more general (though I haven't seen any other apps show this behaviour). Demonstration of different behaviours (if the video doesn't play, click it to open in a new window; seems Imgur prevents looping gifs):