Line-height property in v.0.12.0 (insider build)

The line-heights of headers (#, ## etc.) seem to be several times larger, than previous versions. Longs headers wrapping to a second line look very messy in preview. Fault or feature?

v.0.12.0 (insider build) on MacOS.

Please resubmit this bug report with default theme (no css) and no third-party plugins enabled.