I wonder if the inventor of the hashtag could have patent it, because
are not patentable, since they are abstract ideas.
Maybe an apparatus that recognizes a certain syntax could be subject of a patent, but this would imply that programming languages are somehow patentable as well which contradicts the above.
(See also why couldn't twitter patent the hashtag?)
programming languages are not patentable, since they are abstract ideas.
To begin with, a programming language is not patent-eligible because it is not a machine or process (or other statutory class). When one has a claim formulated as a machine or process (or other statutory class), then one can ask whether it is too abstract or not.
The machines associated with a programming language are the language's compiler and runtime. While the general concept of having compilers and runtimes is old and known, sometimes there are novel features of these that crop up and in such cases they are widely thought to be patent-eligible.
Likewise, a "hashtag" itself is not a machine or process. First one must formulate as a machine or process. For example, one can consider a search engine as a machine that identifies hashtags in a corpus of data and indexes individual records by any of the hashtags that may be embedded in such a record. A claim to such a machine would probably be patent-eligible even by today's stringent standards.
It’s getting harder and harder to patent things can be reduced in a judges mind to an abstract core concept with “nothing more”. And easier to invalidate.
Using special character to delimit a searchable keyword was probably not novel and nonobvious when conceived of by Chris Messina (see hashtag Wikipedia page) in 2007. However I don’t necessarily see it as an unpatentable computer language.
