This is probably a very stupid question, but I am just not sure which solution is the most elegant and the best(most performant) way to go in the following scenario. 

I have the following tables:

Customer, Company, Meter, Reading

all of the tables above the line are supposed to be linked to one or more records of a "Comment" table. Which is the best way to model this relationship?

I am seeing two solutions here:

1.) use m:n relationships: CustomerComment, CompanyComment, etc. -> easy to extend later on, but a lot of new tables
2.) use 1:n relationships: Comment table has a field for the PK of the tables above (Customer\_id, Company\_id, ...) -> minimal table approach, but "harder" to extend since I would have to add a new field to the comment table whenever there is a new table that needs to be have comments

The target is a modular application, which may or may not have any of those four tables.

Which one is the better one - or are there more? 

Thanks!