Can we use `$(...)` instead of backticks?

Could this get a linebreak?  I think:

    HTTP_FILTER_MODULES=$(echo $HTTP_FILTER_MODULES | \
       sed "s/$HTTP_GZIP_FILTER_MODULE/$HTTP_GZIP_FILTER_MODULE $ngx_addon_name/")

would work.

And could this get a comment?  Something like "make pagespeed run immediately before gzip".