In his 25-page response, sent through his lawyer Anshuman Sinha, Thackeray denied the allegations and said he would neither remove the posts nor apologise or pay compensation.
He maintained that his posts did not name Satish Salian and did not contain any defamatory statement against him.
Thackeray reiterated the central line of his September 16 post: "I have never met or known Disha Salian."
He also referred to his call for the official re-investigation into Disha Salian's death to proceed.
Thackeray questions allegations
Thackeray's response argued that the legal notice sought to connect his posts with the broader controversy surrounding the case, including a complaint, court proceedings, media reports and political developments.
He also pointed to what he described as differences between Satish Salian's earlier public statements and his more recent position on the case.
At the same time, Thackeray said he would not "engage in a personal exchange with a bereaved father" or speculate on the reasons behind any change in position.
The ₹500-crore demand was described in his reply as "frivolous", "arbitrary", "speculative" and "intimidatory."
Salian's lawyer says 'evidence' will go to CBI
Meanwhile, Satish Salian's lawyer Nilesh Ojha said a CBI officer from Delhi had reached the agency's Mumbai office and that Salian would hand over a pen drive containing what the lawyer described as "evidence."
According to Ojha, the material includes a video-recorded statement from an alleged eyewitness who claims to have seen Thackeray and others at the scene and alleges their involvement.
These allegations have not been independently verified.
Salian's legal team has sought action against Thackeray as well as former Mumbai police commissioner Param Bir Singh and other police officers and witnesses.
Disha Salian case under CBI investigation
Disha Salian, 28, died in June 2020 after falling from a residential building in Mumbai. She had previously worked as a talent manager, including for actor Sushant Singh Rajput.
The circumstances surrounding her death have since been the subject of renewed legal and political scrutiny.
A CBI FIR was registered following court directions for a fresh investigation, and Thackeray's name has been included among those whose roles are to be investigated. Being named in an FIR does not by itself establish guilt or wrongdoing.