Is there any word on this page that jumps out as the most popular?A well-known word for the combination you requested is 'defensible'.
What is an example of a interesting word that starts with 'd' and includes 'sib'?Ranking as the most unusual word on this page is 'dorsibranchiata'. According to the Oxford dictionary, 'dorsibranchiata' is defined as "A division of chætopod annelids in which the branchiæ are along the back, on each side, or on the parapodia. [See Illusts. Under Annelida and Chætopoda.]".
How many possible words can you make using the combination specified?You can assemble 34 words from the specified letter combination.
What's the longest word you can make with this list?The longest word derived by Dictionarypedia is 'depressibilities'. It has 16 characters.