scenario where ghost memory is annoying

[disconcision]

not a bug, but an interesting scenario several participants encountered.

Starting from this state:

what we want to do is move the parentheses over and replace the arrow with the comma (we want to do a few other things too but those aren't relevant here):

it feels perfectly reasonable to approach this from left to right; that is, insert the comma:

then delete the paren and the arrow:

this leaves this awkward tween state that people hated; the paren remembering its position stops the grout on either side from merging.

If you just go put the closing parens where you want it, it all gets cleaned up, but the tween state distracts people.

deleting the arrow, inserting the comma, and then deleting the parens works better, but feels less natural:

[disconcision]

Dupe of #160