Unless you do something so overwhelmingly stupid that you make a gun unsafe all you need to do is be able to explain why the modifications were made. That and avoid things that make you look like an idiot. "Smile wait for flash" is a funny joke but not something that's going to endear you to a jury.
Hi there. Are you sure this is accurate? I believe in some states if you find yourself in a courtroom, attorneys will tear you apart if you're in unfavorable states such as CA, CT, MA, etc. mainly claiming that modifications to your pistols caused bla, bla, bla. I'm also a newbie and will be using my M&P 9 for carrying once I'm comfortable with it. I was told the best thing to do is leave it stock and if I want to explore different modification then I could always purchase another gun and have at it. Other than a removable stipple back strap, I have no modifications to my pistol. Also, if I ever had to engage a target, I kind of like the stock trigger pull to give me that tenth of a second to make sure this is what I want to do or to give me a quick moment to hold off if someone else were to come into my line of sight. Anyway, to each their own. I'm still learning here, but I think that's best for me and other newbies. Who knows, with more experience I may change my mind.