HCPL3700 - 220V sensing circuit
Yes, not only is R29 OK, I think it might be mandatory. Take a look at the graph below from the data sheet. It indicates that the value of the series resistor affects the detector's switching threshold. It's hard to tell from the graph which curve to use. Suggest you use the 100K and then measure the voltage where the detector changes state. Tune the value of R29 until you're happy with the voltage threshold.



(Image source: Figure 8 from HCPL3700 datasheet)