What I did was not the same. I did the followingI did a quick test abou
t the ditto thing:
First pair: Blaziken (M) (HA) + ditto
Result: F/E/M/M/R(23)/F
Second pair: Chespin (M) (HA) + torchic (F) (HA)
Result: F/M/M/M/R(23)/F
Conclusion: ditto does not affect this method (at least as far as stats are concerned. It might be different for HA male + ditto vs male + HA female, but I doubt it). Unfortunately I forgot to make note of the genders and abilities of the hatched torchics (I think they were both male though. I usually notice females).
Also, concerning shinyness- we only know that masuda shinyness is locked. To prove all shinyness is locked we would have to reset a non masuda shiny, reset and possibly change the parents, and get another shiny.
I used Magikarps as test parents.
Baby Magikarp: M/M/F/x/M/M (used in all cases)
F Ditto: x/x/31/31/x/x
M Riolu: 31/31/31/x/31/31 (Perfect)
Baby Riolu: 31/31/31/x/31/x (misses Perfect Speed)
Different Ditto:
F Ditto: x/x/31/31/x/31 (has Perfect Speed)
M Riolu: 31/31/31/x/31/31 (Perfect)
Baby Riolu: 31/31/31/x/31/31 (Now it is Perfect)
As you can see, something went wrong. For some reason, Speed was inherited from the Father, instead of the Mother. So Ditto did something weird here.