Just to have a differing viewpoint represented.
Addressing questions and answers
The stated reason for stripping politese Somewhere Else (which I largely agree with) is that while posts are created and improved as a human interaction, their main function is as a long-lived informational resource.
If a Q&A site is performing it's job well, many more people will interact with the content by
- finding it through an internet search
- skimming the content to evaluate relevance, then maybe reading the question and some of the answers in depth, and just possibly using the information
- going on their way happy to have found an answer or at least content that they didn't waste a lot of time looking at something not relevant
than are involved in the active creation and maintenance of the content.
In this content the politese is just taking up space and slowing down their parsing.
Addressing other classes of posts
Different type of posts have different goals and should be considered in their own contexts. FAQs and How-Tos are probably better without salutations and the like for the same reasons as Q&As. More blog like articles should probably reflect the author's style (meaning don't "fix" it just because their style is different than yours). Even meta-Q&As have different audience demographics and are much more interactive, so perhaps that's a good place to focus on humanizing the interaction.
Do I care all that much if you leave a "Thanks" in your question?
Nah, but don't get me started on "thx".