Search user posts BBCode not always parsed which can misattribute quoted material

When someone clicks on the number of posts shown in the members profile, the output shows the first 300 characters with a 'Jump to post' link.

Depending on where BBCodes fall in the first 300 characters of the post, sometimes the search results render with the BBCodes processed but for longer posts the BBCodes are NOT processed. This can lead to the case where a posted quoted someone else at the start of a post but the search results output doesn't show the quoted material, thus misrepresenting who said what. 

See https://www.phpbb.com/community/viewtopic.php?f=556&t=2547851 for discussion.