i have three ideas, lets start with the small one.
When you click on the green thumbs up button at your own post it will show you the rep you gained from that post. As you can see in the image below this is quite a messy field to look at and not really organized or informative. Its nice to look at the feedback but you can not really see anything else. The first problem is that you cannot see who has given it to you directly from this field. So you have to go to 'setting' and search for it to see this. The second thing i would like to see in this menu is the day of receiving it and the last thing is how much you gained from them.
This could be implemented in two ways: Firstly, like the post of bill, with the amount gained and the user that gave it to you directly after the message. You have to imagine the date in front or behind it to make the picture complete.
Lastly, this could also be implemented like tooltip/infotip (Tooltip - Wikipedia, the free encyclopedia) When you go over the message of the rep, you will see who, when and how much he gave you.
The second idea; A lot of members have 1 or two threads that they keep for all their invites. This means that, most likely, all the rep the gained is given to the first post in that track. If the user gave away a not so useful tracker like Demoniod and you got it from them (so you gave it +1) and after a few weeks/months/years the same user still uses the same thread and has added a super rare tracker you always wanted to be part of. So you apply and get the invite, but you cannot give him rep cause you already gave it to him. It would be nice to have an option to add rep to the same post for a second time. If, in the new situation, you could gave away +5 rep you can now only give 4 cause you already gave 1 in the early stage of his post/thread.
the third is based on an idea that i have seen on the Dutch tech site tweakers.net, they have a similar system as we have with rep. Only with them its called 'karma'. In you profile you can see the following graphic:
Left side(and red line) is the total of karma gained, left side and the little bars is the daily karma gained. The date is below :p
This system shows you your rep growth over time and when you reached it. You could add milestones like becoming a legend or User is a jewel in the rough, User is just really nice, User is a glorious beacon of light, User is a name known to all to this graph to let people see how they did, and if you look back as a old timer look back at your own progress and see when and how active you where/are. You could make this for all users cause the dates are added in the rep database and could be used to make these images. You cannot be as active here as on the dutch site so i should suggest to change the daily rep into a weekly one.