Some people transition gently - maybe they always looked and dressed androgynous, and had a gender-neutral name like Chris or Daniel/le. Some people transition more dramatically, completely changing both first and last name. The old name becomes the "deadname" and to refer to it - and by extension, everything that that person did - is taboo. They get to start again as their "true self".
Who else gets to start again, and who benefits?
*Adults who find Jesus and profess Christianity - all their sins are washed away - they may receive a new name at baptism
*Likewise those who convert ("revert") to Islam, some of whom choose a new identity (name, clothing, habits which may alienate them from family)
*People joining religious orders (Call the Midwife)
*Ne'er-do-wells who join the Foreign Legion, do the bidding of the French Republic for a few years, and gain a whole new identity, complete with citizenship papers
*Young offenders, on reaching 18
*Those in the witness protection programme - not only victims/survivors but perpetrators too - some scary criminals have grassed up someone scarier
*Any woman who, upon marriage, takes her husband's name (and non-heterosexist versions of this arrangement)
With the deed poll system, anyone can change their name for any or no reason; fine. On the other hand, very few people are allowed to leave their pasts behind; indeed, "allowed" isn't really the word - the state has to facilitate it (up to and including facial surgery for supergrasses). These examples are all different from noms de plume (often not very secret ones, from George Eliot to Posie Parker) or undercover policemen (playing a temporary role, shagging activists and fathering children).
A small number of people change names in an attempt to hide a disreputable past (ranging from a criminal record to repeated bankruptcies). Another small number change their names to mark the fact that they have turned over a new leaf - particularly religious conversions - in that they admit to past errors, and take steps to demonstrate that they have changed.
How does transitioning fit into this framework? I'm not sure, but I suspect there may be some parallels that merit consideration. I throw this out there for the wiser heads of Mumsnet FWR to ponder.