It would be useful if kmail had the option of converting texts of emails where the paragraphs are made up of several lines (each line of the paragraph ends with \n) to a paragraph consisting of one single line.

That is, if it were possible to convert the text of a message with fixed word wrapping to one that can be dynamically wrapped, because each paragraph is converted to a single line. This would be useful as an option both in viewing the message and/or in the composer window.

I find that in long email threads messages with fixed wrapping get more and more mangled as the quote nesting deepens. A paragraph looks fine at the first or second level of quoting, since each fixed width line begins with a > or >> etc. But by the fourth or fifth level of quoting the additional quote marks create new lines from the ends of the previous line that did not fit the width, but these extra new lines do not preserve quote depth.

Example:

> A line that looks fine quoted at depth 1. Another
> line of the paragraph that looks fine at depth 1

vs

>>>> A line that looks fine quoted at depth
> 1. Another
>>>> line of the paragraph that looks fine at
> depth 1

This not just an aesthetic/readability issue, but when the thread becomes long enough the kmail composer becomes very slow and unresponsive.

The functionality I'm thinking of would be similar to Kate's `join lines' applied to each paragraph of a statically wrapped email.

Reproducible: Always

Steps to Reproduce:
1. Produce a long thread of emails each replying to the previous, make sure at least one respondent has static word wrapping turned on.
2. As quote depth increases observe that lines from the static word wrapped emails `overspill' on to new lines that do not preserve quote depth. 
3. 

Actual Results:  
Static word wrapping mangles emails when deeply quoted. 

Expected Results:  
Deep quoting does not mangle the statically wrapped text, because a statically word wrapped text has been turned into text that can be dynamical word wrapped, by joining the lines of each paragraph into one line. 

For long email threads this actually slows down the performance of the composer window (e.g. the cursor moves slowly, scrolling is slow and unresponsive, right menu takes several seconds to appear).