Quote:German site Prad.de reports that sources close to monitor panel manufacturers told them that the production cost of a 27" 4K 3840x2160 panel is lower or at least equal to that of a 27" 2560x1440 QHD panel. This drives monitor manufacturers to use 4K panels in monitors that are specified as QHD - when panel supply is low, or monitor demand is high.

The sources did not mention any specific monitor manufacturer or model, but it's highly probable that some 1440p monitors in the hands of customers today use a 4K panel. Obviously you're not gonna get 4K resolution when paying for a QHD monitor. Rather the panel firmware is configured to report its maximum capability as 1440p, and internally scale the input signal accordingly, which may result in reduced image quality.
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When looking closely, visual quality differences could appear in text, which does get smoothed by all modern operating systems, though, so it comes with some inherent blurriness anyway. Media playback and gaming shouldn't be affected in any noticeable way. One potential method to detect such a monitor is to look for the pixel size specification, which should be around 0.23 mm. For a 4K panel that number is 0.16 mm, so if the specification of your 1440p monitor lists that number, it probably comes with a 4K panel.