> .replace(/ (?= )/g, '&nbsp;') is no good for forwarding, as it results in &nbsp; displayed in the message field, so I removed it. 

yeah, that's what I found in my head later on

> Longpress the sent message, click/tap "Forward", the message is still in tact. 

Wow, this looks bad; where could that comes from?

What I don't like with your patch is that it looks more complicated than it should be, and I'm not comfortable (security wise) doing DOM and innerHTML manipulation when we don't need.

I'd like to finish my other patch today but I may have time at the end of this day to have a deeper look here.