In the testcase the character "f" is moved to the left after the load event.
It leaves behind a black dot at the upper right corner.
Created attachment 103000 [details]
Created attachment 103001 [details]
<rdar://problem/8279291> tracks the same thing with <tspan>, probably the same issue
Actually, I think this is a duplicate of bug 6274.
*** This bug has been marked as a duplicate of bug 6274 ***