How to use same email for multiple users

I have a very big multisite. And I got a request to enable option that multiple users can use the same email. I found a plugin “Allow Multiple Accounts” which doesn’t work properly. I should figure out some other solution for that. I know that I could use something like adding +sometext to every email, so it will show different to WordPress. Do you have some other solution, that can be done here?

Get the current page URL (including pagination)

Is there a WP function to automatically get the correct URL of the current page?
Meaning if I just opened a single post, the function returns the same as get_permalink(), but if I’m on a paginated instance of a page (when paginating through the comments), the function returns the same as get_pagenum_link(get_query_var('paged')) would do.