How to replace content in (un) commented line

[zdm]

Try to comment following line in HTML:

aaa --> bbb

Currently produced incorrect HTML comment string:

<!-- aaa --> bbb -->

Expecting result:

<!-- aaa &#45;-> bbb -->

tcomment has settings which allows to set replacement:

let g:tcomment#replacements_xml = {
\   '<!--': '<!-&#45;',
\   '-->': '&#45;->'
\ }

When uncommenting replacement performed in the reverse order.

How is it possible to achieve something similar?

[zdm]

This is possible to implement in post_hook.
But we need to know, what comment type was used.
Is it possible to add used open and close comment to the context passed to hooks?