a close avatar with impostor appears blocky, pixellated, with jagged edges. (see also VWR-3281)
Technically this is because the image used has not enough pixel size.
(to be noted also that the image used is probably square, for a rectangular avatar, and this makes that the pixels appear rectangular).

This is a major problem, as often we have trouble to see an avatar, especially in common situations such as bals, meetings, etc.

possible solutions:
-have a rectangular image
-have a larger image
-have a larger image wilth LOD (larger image for a close avatar, smaller for a far one)
-use impostor at a greater distance was proposed in VWR-3213, but marked won't fix. This makes sense, as using impostor at greater distance would remove its usefulness in most cases (conferences, bals, etc).

• quote of Torley Linden: "As noted earlier, you can disable Avatar Impostors if you choose, or set Avatar Mesh Detail to High(est), which resolves the problem of the avatars becoming blocky too near".

Note that having a better impostor image would allow to use impostor at a closer distance, and gain on lag in some situations where people are closely gathered (like the attendance in a conference).

well, impostor is a very useful feature. But, as most things in 3D worlds, it is a trade-off, so that it brings some inconvenience or its own. However to have a larger image would much better things for close avatars, without adding much workload to the viewer.