Since launch of a new site (Feb 2015), if your question is about Vi/Vim editor or its plugins, you should consider posting questions at the dedicated Vim Stack ExchangeVim Stack Exchange site where it belongs.
However if your question is not about a compatible text-editor with the original Vi (such as vintage-mode in Sublime, evil, etc.), it should still belong to SuperUser, unless it's about Unix shell (such as vi-mode in shell), then post it at the Unix SE. See: What is considered to be vi?
Questions about programming (such as regex), they still belong to StackOverflow.
If you think you posted on the wrong site, flag the question to be considered for migration (not older than 60 days).