A recent project (PM-2898) has added support for DEBUG_1 through DEBUG_5 verbosity levels to WiredTiger, and moved a large number of messages to DEBUG_2 and DEBUG_3. The code that maps Server log levels to WiredTiger log levels currently skips DEBUG_1 since it would previously result in too much output, but that may no longer be true.

We should experiment with re-allowing DEBUG_1, and if there's still too much output, look at which WiredTiger messages can be moved up a level or two.