I occasionally come across content in my feed that I think would be of interest to one of the small communities that I participate in. Think photo or article, not something personal. Is it appropriate for me to crosspost the content? Without asking the OP? What about if I ask but the OP never responds?
Linking between instances is kinda weird right now, apparently. There's no good way to link to a specific post in a way that's accessible for users across instances.
Post whatever you want wherever you want, but credit the source. This is important not just for courtesy, but for archival purposes. It leaves a trail that makes it easier for others to find the original if they want to see other work by the creator or information about the subject.
If it's just a meme, it's probably not going to matter much, but for original artwork or articles, the author should always be credited when possible, and links make that easier for everyone.
I would take it as a complement if it is something I posted and it is a person just adding to a relevant community. Just don't spam post it to several communities at once or within a short time frame.
When you post something online, it’s generally assumed that crossposting might happen (unless it’s posted on a site that specifically doesn’t allow crossposting). I would think that if the OP really didn’t want you to crosspost, they’d explicitly say so in their post. If they don’t, it’s on them, not you.
Generally, I’d say crossposting is fine - but be sure to include attribution if it’s a creative work.