In fact, this problem occurs not just for the progress bar, but the progress itself, e.g. also in the info box 1 is currently never reached even if the descriptive parameter calculation process is finished. The reason for this bug is that the progress is stored in a member variable which is updated after the progress event is invoked. Therefore, the progress variable is always lagging one update behind. This is fixed by changing the order of the called functions.
The fix is done for the descriptive parameter calculation, but also for the pixel and ROI-wise fitting.

Discussion result: Use permissive mode always switched on. No preferences needed.

Discussion result: Feature is useful but not as plugin on its own but instead as part of the statistics plugin (as an additional button like copy to clipboard).

Integrate into F1 help. Make MITK ModelFit Webpage deprecated for manual section with link to doxygen documentation.

It is a useful feature and should be part of the next release.