In communes without private property, there is generally still personal property. Taking somebody's personal property is theft if you had reason to believe their feelings would be hurt by the taking.
Even communal property may be stolen if there are any sort of expectations about one person having temporary exclusive use of that item. Maybe you and I live in a cult compound where literally everything is communally owned, even the cult robes on our backs. Now suppose that when you step into the shower, I take the robe you were wearing, the clean robe you were planning to wear, and all the communally owned towels as well. I have violated your reasonable expectation to have temporary use of those communal items. I have therefore stolen from you. Maybe our cult has a different word for it, but fundamentally I have stolen from you because I've deprived you of something you had a reasonable expectation to possess.
https://en.wikipedia.org/wiki/Personal_property#Personal_ver...
Even communal property may be stolen if there are any sort of expectations about one person having temporary exclusive use of that item. Maybe you and I live in a cult compound where literally everything is communally owned, even the cult robes on our backs. Now suppose that when you step into the shower, I take the robe you were wearing, the clean robe you were planning to wear, and all the communally owned towels as well. I have violated your reasonable expectation to have temporary use of those communal items. I have therefore stolen from you. Maybe our cult has a different word for it, but fundamentally I have stolen from you because I've deprived you of something you had a reasonable expectation to possess.