Is there a way to remove this numbers associated with vertical segments in histograms in QGIS?
I am using 2.18.
It seems you are referring to a Histogram viewgraph which is available when we choose a
Graduated style in the
Layer Properties | Style.
If you do not have to stick with this function, alternative one is in the
Processing Toolbox | QGIS geoalgorithms | Graphics | Vector layer histogram.
Could be too simple, but from your question this seems to fit for your purpose.