Backticks unsafe in expressions

[johnkarlsson]

Expressions such as:

lcd `=expand('%:p:h')`

stop working if one has the following in their .vimrc:

nnoremap ' `
nnoremap ` '

At least so it seems, I know no vimscript, but I tried grepping for similar use of backticks in other plugins I use, and all of them seem to avoid it, so I guess that's for a reason. Not sure what the best practice is here.