BUG: Topic content formatting and style different between edit and view mode

[ilmartyrk]

There is big difference between topic content in edit mode and in view mode.

[ilmartyrk]

Related issues:
#1346
#1207
#1304

[BeccaMelhuish]

Moving this high up in 'soon' and adding 'UX priority' label, as following the support request (re text colour not showing up when published) mentioned in this issue we discussed in the MM with @ssin1901 and @MeelikaH that formatting saving correctly should be a priority as it's very important for certain use cases. (E.g. a local government or umbrella organisation can't be sending things out to their members or citizens with headings all different sizes, it would reflect badly on them, and therefore make them unlikely to use the platform).