Wikidata is a Wikimedia project, which means you may interact with editors from any other Wikimedia project (Wikipedia, Commons, etc.). You should always interact with other editors in a civil and respectful manner, and you should expect to be treated in a similar manner.
When you add to or modify an existing item, you're editing something that someone else created. That's the beauty of collaborative editing. But keep in mind that just as you can edit someone else's work, other people can edit yours. And you have to be OK with that.
When you interact with other members of the Wikidata community, keep the following core policies in mind:
- Respect people, and be polite even if you disagree. Always assume that people are acting in good faith.
- Part of acting in good faith is speaking for yourself. The expectation on Wikidata is that users will use one account, used by a single person.
- Speaking of you, you are allowed to edit information about you and people you know on Wikidata, but you should take care to represent information as accurately as possible and avoid controversial autobiographical editing.
- Avoid personal attacks. Discuss the content, not the people.
If someone makes a change that you disagree with, don't just change it back. This is considered edit warring and, if egregious enough, can get you blocked from editing.
Be polite and constructive. We are all on the same team.
Note: Wikidata is an international project. Please keep in mind that most people on Wikidata aren't native English speakers. Using plain English and being more patient with others will go a long way.
You can find a full list of Wikidata policies and guidelines here.