Joining bounties is optional unless you want to earn some money online.
There are some bounties that requires a neutral or good trust for someone that promote them are only those who are trusted() in this forum when you join signature campaign bounty.
The bounty managers are required to have a clean thread for the bounty that they've manage. Some are using google docs for reporting purposes to reduce spam on their threads.
You can rank up by having a good post and people will merit it and you can use it to rank up your account. Also, having a right amount of activities is also required but it is not that difficult as long you are active posting in the forum unlike the merit part where it is difficult to obtain. I do also add a note that fishing for merit is prohibited.