At least in my community, when you talk about "sql server" it's obvious that you're talking about MS SQL Server. In the same way, postgreSQL is "postgres" and Oracle Database is just "oracle".
That community being people who already know about the brand. I say it every day at work, too, but the OP still has a valid point for public discussion.
I don't know about your culture, but I've never heard anyone use 'sql server' when they meant 'the database server'. You just don't call it that. I also think it's a pretty dumb product name. You might as well call a web server 'html server'.
People not familiar is Microsoft are probably not taking part in a discussion on HackerNews, let alone a discussion of why their SQL Server product was not ported to *nix.