Comments are designed to be temporary clarifications about specific questions/answers and as such are cleared at regular intervals. 

As the [Comments privilege page mentions](https://superuser.com/help/privileges/comment)

> - Comments are **temporary** "Post-It" notes left on a question or answer. 
>
> Comments are not recommended for any of the following:
>
> - Suggesting corrections that don't fundamentally change the meaning of the post; instead, make or suggest an edit;
>
> - Answering a question or providing an alternate solution to an existing answer; instead, post an actual answer (or edit to expand an existing one);
>
> - Compliments which do not add new information ("+1, great answer!"); instead, up-vote it and pay it forward;
>
> - Criticisms which do not add anything constructive ("-1, see previous comments you scallywag!"); instead, down-vote (and provide or up-vote a better answer if appropriate);
>
> - Secondary discussion or debating a controversial point; please use chat instead;
>
> - Discussion of community behavior or site policies; please use meta instead.