Oh, another leftie crocheter!
I’m sorry you had to experience that comment. I’ll second what the others have said above–it’s completely up to you which side you choose to show!
But you also mentioned that you might want to start writing patterns and do pattern tests etc, and that’s where I’ll pop in to say that it might be good to reconsider and turn your work so the “right” side faces out.
(I’ll pop a post in here, in case: Inside Out - #5 by MakesbyMalin)
The reason why I’d recommend doing that is that some patterns using certain stitches might not work for you if you have your work facing “the wrong way out”. Someone who bought my cauldron pattern experienced this first-hand. That pattern uses front post single crochet, back loop only, and front loop only, and since these stitches are made for some of the outside pieces to work, it didn’t really work for her because they ended up on the inside instead (she didn’t know she had the “wrong” side facing out and contacted me to find out what went wrong).
So if you start testing patterns you might find faults with it that other people don’t experience because it’s assumed you’ll have the “right” side facing out, and if you create patterns with the “wrong” side facing out, you’ll either have to mention that in the pattern, or have people sometimes ending up with parts they think are made wrong because they are made in a way that isn’t too common.
Sometimes it’s just easier to adhere to the standard 
I’ll add that I also crocheted “inside-out” for a while, but when I started crocheting everything with the “right” side out, smaller pieces became much easier to create since you crochet from outside of the stitches instead of having to press the hook through the inside of the piece.
No one could figure out how to teach a leftie to crochet when I was young, so I have Youtube to thank for the start of my craft! I’m happy for you that you had someone who eventually made it click for you!
Good luck, whatever you choose to do 