I feel bad I have not had time to post enough about sukkos – too much work in too little time. nyway, getting back to the Rashi on an eved being patur, maybe this kashe is too much of a nitpick – see Anon1’s comments to yesterday's post - but I can also see whole hekesh to women as an unnecessary detail to understanding the Mishna. Who cares why an eved is patur? – the fact that he is suffices to understand why Tevi did not sit in sukkah.
The Ran (based on Yersuhalmi) asks what the big deal would have been for Tevi to sit in sukkah – even if an eved is patur, why can't he do the mitzvah anyway? Some explain this is the issue Rashi is addressing. Had Tevi remained in the sukkah, it might have appeared that an eved is indeed chayav in sukkah, leading to the incorrect conclusion that there is no relationship between mitzvos an eved must do and those a women must do. Rashi presents the reason for the ptur as a means of explaining why Tevi davka left the sukkah – Tevi’s behavior underscored the relationship between the chiyuv of eved and that of women.
In this case the kashe (if you liked it at all) seems better than the answer. Is an eved barred from performing mitzvos lest the chiyuv of women be misconstrued (the Yersuhalmi asks why Tevi left the sukkah but R’ Gamliel did not object to his putting on tefillin)?
See the Rashash on this Rashi for a more significant point that I unfortunately do not have time to blog about right now.