Pressing arrow keys when there's an active selection doesn't behave the same as other editors, text input boxes in browsers, etc

[sinelaw]

From https://discord.com/channels/1469765718953427058/1469765718953427061/1493718041480007730

if you select a region and click the right arrow, instead of putting the cursor on the right side of the selection, it just moves it to the right of whatever position it previously was.

Did not check comprehensively other directions - e.g. left arrow when starting to select from the right, or up/down in multi-line select where start of selection is not on the same line as end (also the column position of the cursor on the next/prev line could differ)