I am aware of the philosophical meaning.

Then you should be aware that the way in which you used the term is not in line with its philosophical meaning.

Stating you wish to approach something skeptically without stating exactly what you are approaching seems sensible to me.

This was not, in fact, your original wording. From your original comment:

I am here in a position of scepticism about the claims and projects this site wishes to advance.

Specifically, you singled out "this site", i.e. LessWrong, as the one whose claims you were approaching skeptically, suggesting that there was something in particular about LessWrong which you found disagreeable. The connotations of your original comment and the ones you are offering now are radically different, even if they may be denotatively similar. The practice of picking up on (and sending) said connotations is a crucial element of any social interaction, so if people are apparently interpreting your words incorrectly, you should take that as evidence that you were unclear and seek to be more clear in the future, rather than waste time defending your original wording. A simple "Sorry, you misunderstood me; this is what I actually meant" would have sufficed.

I didn't say anyone had been unreasonable, I just said I feel unwelcome.

Again, your original wording:

I have to add that this welcoming thread isn't very welcoming.

This is not a statement about your own state of mind; rather it is a claim of what (presumably) you regard as an objective aspect of this thread (whether it is "welcoming" or not). Again, your time could better be spent simply providing a clarification rather than arguing that said clarification is what you said in the first place. No need to bring up "I didn't say this; I said that"; instead, just say "I meant to say that".

As a more general statement: LessWrong as a community places extremely great emphasis on clear communication. Often, we find that a good majority of disagreements can be avoided simply by having all participants state their position clearly in the beginning, rather than having said position remain unclear or nebulously defined, eventually devolving into arguments about the definition of a word, or some such. If you view this thread in light of this, you'll see that none of this is intended as an attack, as you (seem to) have been perceiving it as. We are simply trying to encourage clear communication, and clean up misunderstandings.