I actually had something related to quote flags as well. It was a user error but the error was difficult to detect because of what I think may be an error in parsing unbalanced quote tags.
For example, I often quote an entire reply that itself includes quoted text. In this case I expect the quotes to cascade.
As a quick example
{quote}{quote}
quoted text from reply
{/quote}
reply text
{/quote}
should appear like this
quoted text from reply
reply text
However in a similar situation you may want to simply string a sequence of quotes.
{quote}
quote 1
{/quote}
response 1
{quote}
quote 2
{/quote}
response 2
And this should appear like
quote 1
response 1
quote 2
response 2
However if you make a mistake and instead have the following
{quote}
quote 1
{/quote}
response 1
quote 2
{/quote}
response 2
I attempted to put in the real example of the unbalanced quote here but it totally screwed up the entire reply in totally non obvious ways which in fact basically demonstrated the problem I'm trying to report. I also tried moving the offending tags to both the beginning and the end of the reply but still no joy. What I will do is place the single example in the following reply.
However in this case I would expect the above error to come out like this.
quote 1
response 1
quote 2
{/quote}
response 2
I'm not totally sure that I'm correct as to what the proper parsing of incorrectly specified quote tags should be but the way I proposed places the error in a far easier place to figure out where the error is. When I first made the mistake for the life of me I couldn't figure out why my initial {/quote} wasn't being accepted when there was actually no problem with it but the problem was that a following {quote} was missing.