This paper contains two new results for the quantitative detector of LSB replacement steganography based on a weighted stegoimage (WS). First, for spatial domain steganalysis, a variant of the WS method is known to be highly accurate only when cover images have never been subject to lossy compression. We propose a new variant of WS which increases the accuracy for JPEG pre-processed covers by one order of magnitude, thus leaving behind the best structural detectors which were known to be more robust on JPEG pre-compressed covers than WS. Second, we explain why WS-like estimators can also detect LSB replacement steganography in the transformed domain, and derive a reduced-form estimator for JSteg steganography which has equal or slightly better performance than the currently best JSteg detectors.