When a buffer gets deleted (the \"bd[elete]\" command), it not only deletes the buffer but also removes the split window that buffer was in.
Is there a way to delete
You can add the following to your .vimrc to have Bd work as bd but without touching the window splits:
.vimrc
Bd
bd
command Bd bp\|bd \#
I found this as a useful complement to what Mud answered.