My tenant moved out a couple of days ago, and when I walked through the unit, I discovered that he had removed the curtain and curtain rod, detached the room air conditioner, and caused significant scratches on the hardwood floor from the metal bed frame legs.

You could consider a DSCR loan for the investment property, removing the debt-to-income requirement for a conventional investment property. 

Just in maintenance, PM, and vacancy expenses the $1800 is mostly gone... not to mention landscaping, snow removal, insurance, prperty taxes, cap ex, etc...

As a lender, I look to mange my risk and sheriff sales remove that ability. 

It's all a bit odd as the seller removed the stove right before the POS inspection which then illuminated this issue.

If it's working with no issues let it go and hold firm.

For illustration purposes, you hire a snow removal company, they are ultimately negligent and don't perform the services they contracted and there is a slip and fall incident.

Your tenant is going to get a free attorney, mine was from one of the largest law firms in America, they use it as a chance to give younger attorneys court experience.  

What are common practices to remove them?

If you place an offer, do not remove contingencies on financing or appraisal.