No problem here - I just tried moving a text event on an overlay track so that it started ONE FRAME before the event to be moved, then moving the lower event and applying Post Edit Ripple. The text event remained where it was.

This is in V8.0a

This behavior never happened to me in Vegas 6.0d, only 8.0a. I do a lot of football video for coaches where I am working with about 100-200 10-20 second clips per game. I have text, overlay, video, audio, and music tracks, in that order. I place quarterly results on the text track, and gradient generated media on the overlay track. Now, for example, if I place my cursor at the end of a play using the right bracket key, and use the numeric1(end) key to delete seconds off the end of the play, and then use Ctrl+Shift+F to close my gap, the text and overlay objects located BEFORE the end of the clip, but AFTER the beginning of the clip, move to the left. This is WRONG. They shouldn't move at all. Objects prior to the beginning of the clip don't move and are fine, and the objects after the cut move as expected.

Weird?

I'm not sure this is what your are talking about but you can try that :
Go in Internal preference and search for “Use new event delete ripple logic” option and set it to FALSE.

Internal preference = Menu Options > Preferences ( + Shift Key )