I don't recall what the settings are to get the vBulletin tables to all display the same width, but anyway. If after all the poster data, you inserted a line break and then the following code:
<img src="images/space.gif" height=1 width=165>
That'd mean that the poster column, instead of being a variable-width jumble, would display with a constant width under Opera. FF:WA inserted such a contraption recently into its template, and I put one in at Fool's Gold a long time ago, almost as soon as I started using Opera. Viewing those forums is now far more pleasing to the eye, in my view. If you're not convinced yet, I've attached a screenshot to show what happens currently.
Anyhow. If you feel like adding that to the template, I'd be happy, obviously.
Peace
Aaron