What's the word for "changing the discussion level/style"?

Question

Imagine two people talking about politics, using rational arguments and philosophical theories, and suddenly a third one comes in and starts ranting about the same topic, but from a very subjective perspective.

Or else, someone posts a humorous, yet shallow picture on facebook, related to recent events, and someone else comments, but in a highly elaborated manner.

In general, a discussion could be led for example in an academic way, it could be pub talk, it could be over-emotionalised, childlike, silly, precocious, relaxed, it could be in the style of a BBC interview or a heated quarrel. I would call all these "discussion styles" in lack of a better term.

What is a word (or an expression) for changing the discussion style or conversation level in such a way? Or is there even a better word for "discussion style"? In particular, I'm looking for a technical term possibly used by linguists.

An example sentence for the first question might be "In facebook conversations between people of different educational levels, [?] are frequently observed.", and for the second question "Alice and Bob were discussing politics when suddenly Charlie came in and completely changed the [...]"

Note that I'm not looking for an idiom for changing the subject in a conversation. The subject should stay the same, only the way the conversation is led should change.

I am also not looking for a specific way how the discussion changed, like "escalation".

Answer 1

Change of tone, e.g. quoting The Times newspaper

Turning point will change the tone of debate [...] The death of an MP [Joe Cox 1974-2016] less than a week from the EU referendum has already had a profound effect on the course of the campaign

A definition of Tone:

4. Manner of expression in speech or writing: took an angry tone with the reporters.

5. A general quality, effect, or atmosphere: a room with an elegant tone.

— American Heritage® Dictionary of the English Language

Answer 2

Divergence:

[A feature of speech in linguistics] When the register and stylistic aspects of the speaker becomes apparently different and incongruent during the course of a conversation.

The individual in this case would adjust his speech patterns to be distinct from those of other individuals belonging to another group/social identity.

*Divergence here can be understood as transient and individual/perosnal phenomena, as it is characterised by a creative choice deliberately made by the individual to reflect/represent his/her feelings in a given situation, at a given time.

[Note that, in other occasions, the same person may make an opposite or different choice freely, for quite logical reasons].

Discussion style= discourse style, speech style