Change threat to validity to threats to validity.
Some repetition can be avoided such as "We chose GitHub as our research setting..." is said twice within two paragraphs on page 2.
each hundred comment -> every hundred comments
of Computer Science department -> of the Computer Science department
rephrase "We also gave a short sample consisting 10 examples....."
The tool was build -> The tool was built
fix LaTeX issues of line overflow.
found very poor result -> found very poor results
threat to validity -> threats to validity
conclusion -> conclusions and future work
(Please proof read the paper)
In Section 4.3. RQ3 you mention "our politeness tool". This implies that you created it. Please rephrase.
R2