As someone said in response to another recent question of yours, a word does not have to be countable to be used with "this". "Countable" means that you can count it, you can say "I have 3 of these". "Uncountable" means something that does not come in distinct units, like you CAN'T say "I have 3 waters." (Well, people are always making countable nouns out of uncountable nouns. If someone said "I have 3 waters" people would probably understand him to mean "3 glasses of water" or some other container.)
But that doesn't mean that you can't identify different "bodies" of an uncountable noun. It is quite reasonable to point at a lake and say "this water", as distinct from the water in some other lake, river, or whatever. "Happiness" is uncountable, but I might reasonably say "This happiness I feel from eating chocolate" or "That happiness that comes with a job well done".
The phrase "as of this writing" is commonly used to mean the time when the composition containing those words was written, as in this example. For example if I say, "As of this writing, Mr Jones holds the world record", I mean that that statement is true at the time that I wrote it, but if you read that article months or years later, someone else may have surpassed his record. Of course this sort of statement would almost always be true of a statement about the current status of anything. It stands to reason that conditions could change in the future. But sometimes we want to emphasize this, to say that we know that it is likely that this will change.