I haven't figured out how to "remove" the individual items at the bottom of the screen, however, to rearrange those items, follow the directions below. Note: I'm doing this on my iPad Mini because I don't use the iMore Forums app on my iPhone, therefore, the directions may be slightly different.
1. Select the "More" option (bottom right corner)
2. Now select the "Edit" option (upper right corner)
3. Now tap and hold the tab/icon you want to move and just slide it to the position you want.
If you want to replace an option with one that is not at the bottom of the screen, simply drag it over the icon/tab you want to replace. Anyway, if this is not what you were referring to, I apologize.