In "reliance of the traveler", section o8.7 talks about some acts that constitute disbelief. The ones this question is about are attitudes that treat Islam too lightheartedly or negatively. The examples read (all from section o8.7):
(0: Among the things that entail apostasy from Islam (may Allah protect us from them) are: [..] (4) to revile Allah or His messenger (Allah bless him and give him peace) [..] (6) to be sarcastic about Allah's name, His command, His interdiction, His promise, or His threat [..] (9) to reply to someone who says, "There is no power or strength save through Allah": "Your saying 'There's no power or strength, etc.' won't save you from hunger" [..] (16) to revile the religion of Islam [..] (19) to be sarcastic about any ruling of the Sacred Law
The same notion as (4) is described as consenus on islamQA:
Reviling Allah or reviling Islam constitutes kufr (disbelief) and apostasy from Islam, according to scholarly consensus.
The fate of an apostate both in this world (execution) and in the hereafter (being tortured in hell forever) has been addressed numerous times on islam.se. Curiously, Non-Muslims seem to have an obligation to not outwardly show that they revile Allah, Muhammad, or Islam, and the legal punishment, if he is a dhimmi, seems to be execution as well according to islamQA:
If the person who defames [Muhammad] is a non-Muslim living under a treaty with the Muslim state, then this is a violation of the treaty and he must be executed, but that should be left to the authorities.
(See also this comment on meta.islam.se for a similar sentiment.)
These consequences indicate that this kind of blasphemy is considered pretty serious, so I'm interested in what constitutes those offenses.
Question: what constitutes the kind of "reviling" or "sarcasm" or "defaming" that is meant?
These are not very clear-cut words, and the threshold for when a statement or action becomes "reviling Muhammad" could be criticizing his marriage to Aisha as child abuse and anything less critical does not constitute kufr, or it could be that saying the following hadith is a bit silly already counts as "reviling the religion":
If a fly falls into your drink, dip it into it then throw it away, for on one of its wings is a disease and on the other is a cure. Ibn Majah