In both of our APIs, LiveFeed and Search, we truncate certain post’s summary field for stability and performance reasons. It was recently discovered that the truncation had two problems. The first, which would leave undesired HTML entities in the document under certain circumstances. The second, which could potentially cut off the last word when truncation occurred.
On 2016-10-11 we rolled out a fix which remedies both of these flaws. You should not find HTML entities in the summary field anymore (please tell us if you still find any!) and the last word of a truncated summary should be left intact. Note that the vast majority of posts are not, and will never be, truncated.
Another recent improvement is also related to undesired HTML entities. The tags field, only present in Search API, should not contain HTML as of 2016-09-08.