Please note, the below does *not* stop other forum users from giving you reputation, nor does it prevent you from giving reputation to others.
Click "Control Panel" link (far left-hand side) on forum menu bar along the top -> Under "Control Panel" area (left-hand side), click "Edit Options" link, located under sub-heading "Settings & Options" -> Within "Login & Privacy" area check tick-box "Show My Reputation Level".
Scroll to the bottom of the page and click the "Save Changes" button.
Enabled:
Current reputation level is displayed to others in the forums.
The 5 mostly recently received reputations are listed under "Latest Reputation Received".
Refer to attached screen capture - 2008-01-28_MyForumReputation_Enabled.png
Disabled:
Current reputation level is not displayed to others in the forums.
The 5 mostly recently received reputations are not listed under "Latest Reputation Received".
Refer to attached screen capture - 2008-01-28_MyForumReputation_Disabled.png