Is it possible to stop the indexing of certain parts of an HTML page. i.e If there are comments included within using the HTML Comment Tag
You can customize search crawler and remove all HTML between comment tags. Read documentation here Customizing how crawlers process page content
Or if you use ascx controls (or transformations), you can wrap your comments in <%-- comment --%> and it will be removed from output html. For K# you can use another syntax: K# comments
Although already marked answer, here's an article i did on how to get the smart search index crawler to only index certain sections of a page
I know Anton has already provided you with correct answer, however if you would like to deep dive there is an article written by Kentico support which very detailed and instructive.
Exclude certain HTML elements
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