I haven't sold on eBay in a long time, but sold items on Reverb pretty regularly until a few years ago. It's annoying, honestly, and the bigger Reverb has become the more nonsense potential buyers you have to deal with (this also depends on what you're selling). That said, it does seem to be the most widely used marketplace outside of things like Craigslist and the like. So you're more likely to move your item a bit faster.
With the new tax law, Reverb (and any marketplace) will have to report your sales and issue you a 1099-K if you hit the $600 threshold. I honestly don't know what that is going to entail in terms of filing taxes each year (do we now need to keep receipts to show we didn't have make any income from the sale(s)?) The way Reverb has it set up is if you hit the threshold, they will hold your earnings until you give them your tax information. Just something to keep in mind.
Pricing: I usually spend a couple of minutes looking at the the prices of the item already on the site and price mine somewhere in the middle and accept offers. This is more of a personal thing, but don't price-gouge or engage in "hyped prices." Reverb has made the resell market for flipping gear worse than it was before. Just because you *can* get X amount for an item, doesn't necessarily mean that it's actually worth it or that you should. ¯\_(ツ)_/¯
Does setting a higher reserve price stifle interest?
Depends on whether or not you accept offers. If your price is really high, it might deter some people who may think your price is unreasonable.
Shipping: For the love of anything holy, insure the package for what it's worth. I made this mistake once and ended up being the only time I've had an issue with a delivery. It sucked. Reverb offers postage and "reverb protection" when you sell an item. It just means they'll handle any claims if something happens (I haven't experienced this, so I don't really now how well it works).
Try to be considerate with how long it takes you to reply to messages and offers. If you sell an item, you have to ship within 3 days after the payment clears. Do not ship until the payment clears. You'll occasionally get people wanting to do a down payment or something. Don't.
Reverb tracks the prices of everything. So be mindful of offers or "combo buys" - e.g. someone buys multiple items from you at a lower overall price, but places the offer on one of your listings - which will make it look like that one item sold for much higher than normal and can artificially inflate future prices.
There are some alternatives popping up here and there, albeit with not as much exposure as Reverb.
There's an instagram account called Music Gear Swap where you DM the account with a picture and short description of the item, they'll post it and send people to your account for more info. No fees.
https://www.instagram.com/musicgearswap/
There's also Byrd Finds out of Nashville. He has a website and lists items on consignment (10% fee). Most consignment gear ends up on his @byrdsells IG account, but he's slowly getting more and more over to his website.
https://www.byrdfinds.com/