Based on the rulings of the SE model we shouldn't use neither (pbuh) nor (peace be upon him) nor (Prayers and Blessings of Allah be upon him) nor any kind of expressions like this.
Muslims tend to see calling him simply Muhammad as a kind of disrespect, which IMO and to stay somehow conform with the polices of SE would be using a kind of at least more respectful expression like the Prophet Muhammad or the Messenger of Allah etc. of course if the full expression is quoted in a source that wouldn't disagree with SE polices as far as I can tell. So that would be my midday solution or suggestion:
Calling him Prophet Muhammad or Messenger of Allah and if in a quote take it as is in the source.
I'm not that long active here to say whether it would be easy or hard to make an end to the excessive using of these kinds of expressions of honor for the Prophets, Allah, Sahaba and other honorable people and also greetings like as-salamu alaikum (some also use abbreviations) and thanking like jazakaAllah khairan ... (you may find posts about all of that here on meta) which IMO take a lot of space and in our hearts we know that we would use them, and i don't think it is necessary to post them.
Of course you could oppose my post and say hey you use it the same excessive way. My answer wouldn't be logical either: I see that most of the people do so and if we can find a consensus to make a cleaning action to remove all the unnecessary stuff I'd be the first to join it. And I'm lately really thinking about posting here a Question about this matter.
On the other hand I'm not sure whether this plays a role on the voting behavior: all I usually see we have seasonal activities, so out of Ramadan, Hajj, maybe 'Ashura' and other more or less short occasions the site has visits but rarely new posts (IMO even during that time most of the new posts are already covered to 80-90% so they maybe slightly special cases of answered questions), so only during that time there's a more reasonable voting behavior out of that you may find most of the answers accepted (if they were accepted at all) with 0 up-votes and most of the questions which include a sin in the title down-voted.
Apparently nobody cares about the quality of a post rather than sin and sinner, and sects and sectarianism. But maybe and as said above I'm not long enough active to say that not quoting this expression of honor may play a role in the voting behavior.
Sometimes I ask myself whether Muslims are even too lazy to click to vote here. I mean we really have many great questions but from around 2014 till now it would be hard to find a question or answer with a double-digit voting total which doesn't really reflect the quality of an answer or question, while in older posts you may find much more of these kinds, and I even found answers with many votes which miss a lot of what I would qualify as even a good answer (and I don't think I have high standards).