[tars]

Movie Preferences -> General Tab, Actors filter can be set to Minimum and Maximum number of actors to display.
Same for Directors.
The Maximum number of Actors, Directors and Sets is each 5000. The default is 500.
Why. Increasing beyond 5000 is a major performance hit as MC cross references all actors to all movies.
For example, 2400 movies, and over 88000 actors, I set the limit to 100000 actors. MC took 80 seconds to process the actors for this filter alone, and another 48 seconds to process the directors. (Some actors are Directors also).
At 500 (default), MC was half a second. at 5000 limit, MC took 6 seconds.

That explains it. So sorting actors by alphabet is practically unsupported (because it lists only A) and sorting by numbers are only partially supported.

Here's a slight improvement for Actors.

• Movie - Increase Max Actors and Directors to 10,000 (default is still 500), but if set over 999, set minimum to 2 films to offset performance hit.
  

Thanks, but if it comes with any performance degradation, I don't think that's worth it. I tried various combination of settings and now settled with default values for Actors & Sets, and Max 1500 for Directors with just slight lagging for opening main browser. Currently if I change Max Actors to 5000, opening main browser takes another 7 secs. Setting minimum to 2 movies doesn't make noticeable differences.