I made a friend at GC last year who is from out of country, he and his wife are vegan and I've promised to take them out to dinner one night of the con for our friendiversary! I know Indy has tons of veggie-friendly options, but was hoping for a good suggestion based on personal recommendations for something with a decent conversational atmosphere and a visibly vegan-friendly menu. Libations a plus, but not required. Any suggestions are much appreciated!

Three Carrots! Both locations are great options. 

https://www.threecarrotsindy.com/menu/

Three Carrots thirded. Note that the City Market location is closed on Sunday. I think they serve beer but don't quote me on it. Cafe Patachou has vegan options for breakfast/lunch and serves beer and wine, but the downtown location is always packed during Gencon. If you need to stick downtown, I would say Napolese Pizzeria is a little nicer. Full bar, open for dinner, customizable Neapolitan-style pizza that can easily be made vegan. 

If you have a car, or are willing to Uber/Lyft/taxi, consider The Sinking Ship. Lots of vegan options, plus craft beer, whiskey, etc.

Yard House is also a good option. Their menu has an entire Gardein (a brand of a vegan protein substitute) section, in addition to general items that I think are vegan, so it is easy and clearly marked. They also have a great beer selection. 

India Garden and Haveli have a lot of vegetarian food, much of which can likely be made vegan (though I'm not vegan, so you'd want to call and confirm to be sure). 

I second Three Carrots, and the Sinking Ship is a good late-night option. Also would add Garden Table on Mass. Ave.

Thank you so much! These all sound great. I will have my car so a bit of travel isn't a deal breaker! I appreciate the recommendations. 

Other options include the Garden Table and Public Greens