The quick answer is that we can only display what Facebook's API returns in their search API.
technical and long answer is that while Facebook supports hashtags
internally, they have yet to release full support in their developer API
-- meaning third parties (like Tagboard) don't benefit from their
hashtag search indexing. Instead, as a stop-gap, Tagboard utilizes the
standard Open Graph Search API and searches for hashtags using normal
keyword strings (e.g. #WhyWorkAtTagboard is converted to
WhyWorkAtTagboard). After we receive a search results, we then strip out
any that do not contain the actual hashtag.
Facebook only provides a 'sampling' of public posts in their API
results; of which it is uncertain what characteristics constitute a
viable candidate. We simply have no way to know for sure what kind of
results we can expect from Facebook.
Finally, we elect to not
display certain results we receive from Facebook because they're
returned to us without original attribution as shared posts, meaning we
do not know who originally published the post. - Tagboard Support