These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Sleepless in Ponyville revealed that Luna can enter in other pony's dreams.
Memetic Mutation: Since this fanfic gained popularity, it seems almost required that if you have Luna show up in a comedic fanfic, her abacus will either be nearby or mentioned. Grimdark and Sad fics don't need to follow this, but some have. The abacus has also appeared in several drawings as a background prop.
Moral Event Horizon: It's been suggested by some readers that Luna crosses this in "Luna Versus the Dreamlands 2", when she imprisons Discord within a dream within a dream within a dream as a statue in a white, featureless expanse. The resulting time dilation would have him passing millions of years within that space while time flows normally outside. In her defense, Luna did this to ensure he would not threaten Equestria again. Still, as the page says...
Given what Discord is suggested to have done to Equestria before his first imprisonment and what he did upon his escape, Luna's actions are arguably justified. Especially given the limited number of options when dealing with a being as powerful as Discord is. Luna might have been harsh in her punishment, but this troper doesn't believe she was evil. More of an Anti-Hero doing what no one else would and deserving of a What the Hell, Hero?.