Multiple attachments in # implemented in v.52.00, currently in Beta https://github.com/andstatus/andstatus/issues/456
Showing multiple attachments in incoming notes should work for all Social networks.
But sending for now was implemented only for # (tested to work)
and for # # (needs fixes for image posting yet... see https://git.pleroma.social/pleroma/pleroma/issues/1171 ) https://gnusocial.no/attachment/1735455