autocomplete of user names

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The autocomplete of user names in comments is useful, except that it prepends the text used to search for an ID. For example, if I'm looking for Nittany 7, and start autocomplete by typing @ so that I have @nitt, then the name shows. However, if I click it the text then ends up @Nitt@Nittany 7. So I have to manually delete the extraneious text.