Only release I remember reading left to right was an old Akira american edition. To be honest, the editing was well done, with the mirroring edited so you couldn't tell the difference at a simple glance.
That, combined with translated onomatopoeias served the purpose I figured the original editors thought of: To deliver the manga experience to a bigger public. Seeing that the trend now is towards weeabooness, releasing like this right now would be editorial suicide.
Now, I checked, and all of my purchased and scanned manga, both hispanic and american, adopted the right to left. I figure that since it involves such hard work of fixing every panel just to correct something you can get used to read in a few minutes wasn't worth it.
Still, I prefer it this way. You get used to reading right to left, and it's hard to let it go.
It actually gets confusing at times. It took me a few mistakes reading Y the last man to finally read it correctly.
Speaking of, I wonder if elevens that scanlate comics flip them, or they are reverse weeaboos...
"I read my american comic the way it was meant to! left to right and original english!"