What is the difference between a command on the basis of recommendation and a command on the basis of obligation in the Sunnah, and is the default for commands to be obligatory unless there is an indication that diverts them from that?

The command of the Prophet (peace be upon him) entails obligation unless there is an indicator that diverts it, and this is the view of the majority of scholars. Evidence for its predominance includes Allah's statement: "And let those who oppose His command beware, lest trial befall them or there befall them a painful punishment" (Surat An-Nur: 63), and His statement: "But no, by your Lord, they will not believe until they make you judge concerning that over which they dispute among themselves and then find within themselves no discomfort from what you have judged and submit in [full] submission" (Surat An-Nisa: 65), and His statement: "And whatever the Messenger has given you - take; and what he has forbidden you - refrain from. And fear Allah; indeed, Allah is severe in penalty" (Surat Al-Hashr: 7). In a Hadith narrated by Al-Bukhari: "All of my followers will enter Paradise except those who refuse." It was asked, "Who are those who refuse, O Messenger of Allah?" He said, "Whoever obeys me will enter Paradise, and whoever disobeys me has refused." Thus, a command in its absolute sense indicates obligation, and if there is an indication that diverts it to recommendation or permissibility, then it is carried upon that.