I recently came across this surprising behavior involving " and ! in bash:

guy@guydell:~$ echo arbitrary echo
arbitrary echo
guy@guydell:~$ echo "!e" #unescaped history expansion
echo "echo arbitrary echo" #unescaped history expansion
echo arbitrary echo
guy@guydell:~$ echo "!e" #escaped history expansion
!e

Notice that in the second to last line, history expansion does not occur. This is because I used a to escape the !. However, the remains in the input to echo. This is not the case with e.g. ":

guy@guydell:~$ echo """
"

This behavior is documented:

If enabled, history expansion will be performed unless an ‘!’ appearing in double quotes is escaped using a backslash. The backslash preceding the ‘!’ is not removed.

I was curious as to what motivated this design decision. I would expect that, if a were to escape a character in a string of text, the would not be included in the string. Directions to an archive of an email list (which is where I assume this would have been discussed) or an excerpt from the discussion would both be appreciated.