What's the maximum comment size in JIRA?

[MattS]

And do large comments affect performance? (I expect they do somewhere based on https://jira.atlassian.com/browse/JRA-28519)

And can I really set a maximum size for comments in JIRA? https://jira.atlassian.com/browse/JRA-38732 says "jira.text.field.character.limit is respected for description, environment, comments." but it's not documented. Does it work as advertised?

[crf]

Comments don't usually have a significant impact on performance, but if you're loading an issue's data then it should come as no surprise that 10 comments of 100M each take longer to load than no comments at all.  I would expect this to matter most for public sign-up systems where there is more exposure to spam and other abuse.

The setting you want is jira.text.field.character.limit, and while it may not be independently documented, it is one of the things listed in the "Advanced Settings":

Screen Shot 2015-05-22 at 6.14.21 am.png

[crf]

I should add that mail loops have also caused problems with this in the past due to the sheer number of comments that got created, but that these days the view issue page doesn't load all of the comments by default, so the exposure to that one should be much less.