The 4th implies the 3rd. If I think you're wrong, I'll say you're wrong--with reasons. Adding some additional words like "in my oh so humble opinion I think" doesn't change the fundamental meaning. (And I have absolutely criticized well-known people's opinions on public stages.)
It absolutely changes the meaning. Perhaps, in some cultures or subcultures, showing humility has a weakening effect but I tend to avoid those places nowadays, or at least push back on them.
A subtle feature of language, at least in English, is that prefacing things with "I think" or "I feel", while displaying humility in personal conversations, has the effect of devaluing your own argument if done in excess. If you are perceived to be forever apologizing for your own opinion, nobody is going to take you seriously, because what you ultimately lack is confidence - and if you're not confident about what you're saying, why should I be?
It is, and should be, OK to actually strongly state a position you hold, especially if you can back it up, and especially if the person you are responding to is going to take your criticism well (which the author did know).
"Joe is an idiot" is very different from "Joe is wrong" especially when Joe is definitively and demonstrably wrong (which he was in this case, the author demonstrated clearly and succinctly how to do something Joel said was difficult to do).
Adults are (or should be) also capable of determining when a talk is a string of personal attacks, or a mature but critical response (critical meaning evaluation, not negative). If every other phrase was "Joel has his head in his ass" then NumFOCUS would have certainly had a case; that wasn't the case here.
Do you forsee a circumstance where forthrightly saying "The state of the world is X" implies "The state of the world is X but I don't believe it"? That seems like a difficult state of mind to achieve.
I'd buy that there are subcultures where prefixing "I think..." is a gesture of respect. But the CoC's I'm familiar with generality don't demand that the speaker aligns with a specific culture. Often they encourage accepting multiple cultures.
Indeed, I'll go as far as saying that a big part of conferences is encouraging different subcultures to listen to each other.
I often find myself using the phrase when something clearly is a matter of opinion rather than an absolute fact. I'm not going to say "I think the earth is a spheroid." But I might say "I think we're going to see more heterogeneous computing." But it's mostly an anti-pattern and I often edit them out when I'm writing.
