Let’s look at important things here –
Mercury - Mercury represents communication skills, marketing, calculative ability, younger siblings, hobbies, skills with hands, intelligence, quick decision making, logical thinking, youthfulness etc.
Hasta - Hasta is nakshatra of healing, health care and skillful people. It also represents hard work. For more info on Hasta, please check this link - https://www.astrosaxena.com/hastnaksh.
Virgo - As Hasta is a part of Virgo, Virgo sign and its representations also become important. Virgo is the 6th sign of zodiac belt, hence it represents almost all the things which are represented by the 6th house of horoscope like Debts, Diseases, Obstacles, Serving the under-privileged, Service Life, etc. Besides this, Virgo represents analytical or critical nature of people, being perfectionist and healing abilities. Virgo's basic representation is the lady coming in boat with wheat and herbs in her hands. So, Virgo is basically a sign of healing. Virgo consists of next set of 2 and half nakshatra. i.e. Uttara-Phalguni, Hasta and Chitra. Virgo's lord is Mercury.
Moon - As Moon rules Hasta, Moon's position and dignity is important to know about the overall functioning of any planet in Hasta/Virgo.
Mercury - As Mercury rules Virgo, Mercury's position and dignity is important to know about the overall functioning of any planet in Hastai/Virgo.
Houses Involved – Also, we can’t afford to forget the houses involved as a planet can be ruling different houses and sitting in different house for every person as per ascendant and planet’s position. To know overall affect, we have to consider the houses involved as those areas of life are being impacted.
Interpretation of Mercury in Hasta Nakshatra – This is where Mercury is strongest as it is in its own, mool trikon and exaltation sign. Moreover, Hasta is where Mercury gets its highest exaltation because it is ruled by Moon, father of Mercury. It means person can expect best of results of Mercury here. They can be very articulate and perfectionist in their communication. They can be seen as clever business people or Lawyers who can be excellent with their drafting skills. They can be clever or almost cunning with their money dealings. They can be hard working and ambitious. At the same time, Hasta is closely connected with healing and health care. As Mercury represents Communication, they can be seen as best counselors or healers. They can be good with healing people through hands, i.e. Reiki. But again, problem will come-up in relationship matters where they can expect perfection from other people and may be very controlling. Overall, this position can be very good for business and communication but they need to learn to manage relationship in a way other than like a business.
Role of Moon – Moon placement is important to guide Mercury in right direction, being Hasta's lord.
Role of Mercury - As we are trying to interpret Mercury only, we need not to look at Mercury's placement separately.
Other Factors – And of course, we need to consider conjunction, aspects, house lordship, house position and dashas etc to know the exact results of Mercury in Hasta. So, we always need to take a holistic view of chart rather than just 1 planetary position.
Conclusion – So, this is how I see Mercury in Hasta can work in a chart.
Hope this helps. Please post any comment or query you may have.