In my opinion, links should only be added if they are immediately relevant to the question, regardless of where the links point to (can be Wikipedia or Canonical or whatever that is most useful and relevant). Also, adding a hyperlink does in fact affect the readability of a post because it causes the hyperlinked text to be colored differently from the unhyperlinked text. For a post on the main site (but not the meta site), the hyperlinked text also gets underlined when you mouseover it. This means adding hyperlinks will draw attention to them, so we want to make sure the attention expended is worthwhile.
For this particular edit, the links to the Wikipedia articles for Ubuntu 14.04 and HP Pavilion notebooks are not immediately relevant to the question. Therefore, such links, when clicked, have drawn attention to information that is not useful and wastes time. The proposed Wikipedia links are therefore harmful to the post and the edit should be rejected if the addition of the Wikipedia links were the only modifications in the edit.
Unfortunately, we can't reject or accept parts of an edit. For this edit, I think the good from fixing grammar and punctuation and removing noise outweighs the bad from adding the Wikipedia links. Therefore, I would have chosen "Improve Edit" and then remove the Wikipedia links.