Can confirm:
sftp> cd Foo\ \[bar\] sftp> ls hello.txt sftp> get hello.txt File "/home/lfaraone/Foo [bar]/hello.txt" not found. sftp>
Can confirm:
sftp> cd Foo\ \[bar\]
sftp> ls
hello.txt
sftp> get hello.txt
File "/home/lfaraone/Foo [bar]/hello.txt" not found.
sftp>