clip_near can be lower, even 0.1. But you then need to change clip_far also, otherwise you won't have a properly working z buffer anymore.
For today's 3D hardware, with a 24 bit z buffer, we recommend not to use a lower value than 10 for normal levels. Only in special cases, when clip_far is very low, you can make clip_near lower as well. The problem is not the absolute value, but the ratio of clip_near to clip_far, which must not exceed the 24 bit accuracy.
I'm moving this to "Engine" as it's not a bug report.