In an embodiment, a data processing method comprises a first computer obtaining access to a digitally stored video program and causing playing the video program in a player window of a second computer, wherein the player window includes a linear graphical timeline representing the video program; the first computer receiving from the second computer location input data specifying a point in the video program and determining a time value of the point in the video program; receiving comment type input data indicating a particular comment type among a plurality of available comment types; receiving comment input data; creating and storing, in electronic digital storage coupled to the first computer, a record that associates an identifier of the video program, the time value, the comment type input data, and the comment input data; causing displaying, in the timeline at a position that is proportional to the point, a marker having a particular distinctive appearance from among a plurality of distinctive appearances that correspond respectively to the plurality of available comment types.