It is not intentional when a post stated "I've read somewhere about ____ and _____ about ____ when that user knows that it is not his/her content in the first place unless he/she will provide the link where he/she read that content from and it won't be a plagiarism as result.
Hmmm it still is. Could be the user " forgot" to cite the source or didn't remember the exact source they got the in formation. But that will be for the moderators to decide.