No, it's not.
The forum search does not give an advantage to users to help them win games, therefore it is a perfect Supporter feature.
one advantage that i think about this feature:
if you search more, you learn more...
this game is somewhat complicated to new users, and with their limited knowledge, faster forums browsing is essential to anyone who have a thirst for knowledge... thus, helping them understand more about the game.
for example: the training process here in BB still puzzles me.
with the search tool, i can easily search all posts/threads about training, eventually understanding the training much faster, and doing all that i have learned rather than still finding the right thread to read.
having this option for supporters only, IMO, gives a BIG advantage and should be open to everyone... just like any other forum sites.