Sorry, just saw this. Sorry for the (very) delayed response!
It is possible to remove outliers, but generally this is done when calculating statistics. That is, when calculating the mean/median and uncertainty for a selection, iolite automatically does outlier rejection if you have set this up in iolite's Preferences (in the Stats section). This doesn't remove the point from the time series. Rather, iolite calculates the mean/median without outliers. That way, you can change the calculation and no data points are permanently removed.
If you would like to 'remove' a data point from an image line, you can do this via smoothing. For example, you could add a Box row filter to your image and it would smooth out the outliers. You can adjust how much smoothing to apply using the setup button (the slider adjusts how far before and after each datapoint is should average values).
If that doesn't answer your question, please let me know.