There's the well-worn discussion of cases where someone did a mitzvah when the rabbis said not to, e.g. blowing shofar or taking lulav when the otherwise-right day was shabbos.
This is usually linked to the discussion of if someone said Shema after "midnight"; do they not get the "proper mitzvah" credit, or did the rabbis cancel out the mitzvah altogether.
While both of these involve the principle of rabbinic power to cancel a mitzvah obligation in a passive manner (shev ve'al taaseh), there's a pretty serious distinction: the shofar/lulav fellow is committing an act of commission, being active when the rabbis said to just sit there and do nothing. The fellow who spaced out and missed Shema for six hours sinned by omission -- they did nothing.
It would seem like a reasonable policy (and yes, it's baalabatish) to suggest that if you get up and cross a line the rabbis said not to, they will cancel out your mitzvah. But if you just did nothing, it's hard to say the rabbis then order you to keep doing more nothing!
Does anyone suggest such a sevara, and differentiate between the cases?
