The developers do their best to bring you a stable program. However, with many interacting features and several platforms to support, it’s easy to overlook the occasional issue.
A bug is a problem in Krita’s code that is reproducible and fixable. Before reporting a bug, first check if your problem has been discussed before. You can discuss your question on the forum or on IRC. There is also an active community on Reddit. Do not mail the Krita Foundation or developers directly for support.
Note that the IRC channel is not a company support channel: it’s a place where developers and users of Krita discuss Krita’s development. It’s a place where you can ask questions, but you have to be patient, and you might see other discussions going on at the same time. Krita’s IRC channel is not logged, and if you leave, we cannot answer you.