Er, I forgot to mention this - I thought about it when I was writing the expression (not the post) and forgot to mention it in the post. There is one (possibly) problem with the comments section. I'm not sure exactly how it works, but basically, it goes like this, if you've never
edited the comments, then it doesn't get stored (locally?) in the database.
EDIT:Is this a custom column? I can try and duplicate it if you give me the column name/settings. Also, I have no idea what sideheader is?
It basically means that in order for the regex to work and for calibre S&R to find the HTML, you have to have first opened up the HTML source side of the comment and (maybe) edited it. I've never experimented with it myself, but I know I had problems in the past and happened across the thread semi-recently (within the last few weeks) while I was exploring the forums. I read it, stored it in my long-term memory and most of it's a haze beyond knowing that's what the problem was. I haven't spent the time to experiment and find out how to 'fix' the issue.
Found it.
Try editing the comment in plain text, see if that works, if it doesn't try editing in the HTML source (add a space or something to either). If it doesn't work after that I don't know what to tell you.
As for mass S&R? possibly doing a S&R replacing ' ' (space) with ' ' (two spaces) might modify and store the HTML locally. I really don't know how it all works and haven't sat down to see what will affect it.