How many times have you wanted to search a store inventory quickly instead of reading through the whole list? Perhaps ideally there would be a new command that "applies" to readables and searches the output.
grep [scroll]
scan [text]
apply search [text]
On the other hand, satisfactory to just support jumping back in message history per search results.
Alternatively, in the client only, search the Messages window (probably configurable depth) and put results in Critical Messages.
Ideally, search is not case insensitive by default (possibly if search pattern is all one case).
Diff: