If you've got a colleague who just can't stop messing up whitespace, then you may want to politely suggest (or surreptitiously install) Laurent Georget's ShowSpaces (GitHub: guiniol/vim-showspaces) plugin.
It's a small albeit focused plugin that shows whitespace at the beginning of lines. You can change the highlight colour and turn it off -- the full details are in the readme and bundled documentation.
CTRL-] will follow a tag and open it in a new column. You can keep doing this to navigate further down, so you end up with stacked columns. You can press
CTRL-t to go back or
CTRL-, to shift all columns to the right.