Comments are meant to be so lightweight that this is not something contained in the core engine. Comments are also sometimes not loaded on the initial page load if there are too many, which causes problems with things like this.
However, on the Stack Apps site, a site for standalone apps and browser scripts to enhance the sites, you could search for an existing script or request one be written.
I am familiar with SE Modifications -- Username autocomplete in comments, inline revision source, and utility linksSE Modifications -- Username autocomplete in comments, inline revision source, and utility links which makes the timestamp of a comment become a link to the comment, but feel free to search for others.
