Well yes it was directed in your general direction, sort of like buckshot.
From my side of things, I rarely know when a person is flirting with me. Strike this up to high functioning autism (which I now carry a certified diagnosis), or you can strike it up to my not being very interested in dating, or being in a LTR (not currently, but in the past).
The answer to knowing why you don't notice may not be just one thing. For me its multiple answers which combine to a general "I don't see it".
As for your flirting with other people, you have to ask yourself why it is so important that you do. Some people are naturally flirts, others, such as myself flirt only with those guys who I end up in a bad romance with.
Maybe something that connects is your ability to have pet names for a mate. I know with myself it feels forced to call my partner "dear" "sweety" and all of those other names. I think there is a connection for myself, perhaps this is similar to your experiences?
Human social interactions are highly complex all due to that forebrain having developed eons after the reptilian/animal hind-brain where all of the biochemical reactions that lead to the mating dances and procreation arts - ya know the summoning of the stork ritual, or the simple name of Sex.
Humans have developed over a few billion years, we still carry alot of those other ancestors to homo=sapiens with us, and largely the whole "how we pick a mate" is biochemical.
I have the 20/20 hindsight thing going on when a guy expresses interest in subtle ways. For me its biology, psychology, sociological approaches which I developed due to how I was raised, what era I was raised in and slight autism.
Being comfortable in your own skin means that between you and that individual that you are flirting with there is some sort of connection.
One problem with the modern world is that we cover our own scent with unnatural chemicals - colognes, aftershave, hair gel, scented deodorants, scented soaps. Humans do still rely on the scent of potential mates to determine viability of offspring. Just because your gay does NOT change that seeking of viable offspring scent locator. It just means that you seek the gay pheramones - which science has uncovered that such exists. Google it.
Visual cues beyond the surface "This guy looks hot/cute" also play a role. Somewhere in the Evolutionary family tree humans didn't talk much. they relied on body language to communicate. Oddly enough flirting behaviors are largely body language. Such as leaning toward a person you are interested in, mimiclking their movements.
And facial recognition of emotions is another aspect. A computer was developed that detects winking - but it is unable to determine what that wink means because the other cues are an alien languages which frankly humans have yet to scientifically determine how a certain type of wink signals what emotion.
Its like the "lie tell" where some people can, with a great degree of accuracy, know when a person is lying. Such as a person looks upward when seeking a data file (recall) and looks down when lying. Well most, I happen to do it backwards -BUT my eyes scan back and forth when seeking a data file (memory/recall) and look straight ahead when figuring out how much truth to include with a falsehood to make it sound plausible.
There are similar "tells" in all forms of human communication.
Verbal "flirting" is hard without the face and body. Which is why so many relationships land up on the rocks when the couple relies on text messaging or emailing for communication. Words are simply not enough.
Nor is silence and hoping your partner can read your mind (body language). While obvious facial expressions do communicate megabytes of data, there are billions of subtle facial expressions that flicker in a second across a face that the brain picks up, but most people are not able to discern all of that data and reach a correct or mostly correct interpretation.
And if you are dating individuals from different cultures the problem is more complex.
Unless it is blatant, undeniable flirting behavior its going to be hard to determine. And if your not feeling it (comfortable in your own skin) then flirting is going to be force, and false which is a lie that others will pick-up on. Well most others. Go ahead, flirt with me, might as well scream at a brick wall. You'd get more feedback from the wall than me.
If it is boiling down to meeting new potential partners, then go with what feels right and natural to you. If the right potential partner comes along no matter how deeply involved in your work or whatever the message will be loud and clear.