Length of a comment max 5000?

Hello Leonid, on pc with Firefox, I tried several times, here is the text in question, I had to post it twice in the end. We talk about comments, right?

"Hey Vavillon, nice illustration! Yes, it's a very good idea, you check and everything is reset, a reset button, anything but something. In another post, I was just wondering if there was automatic pruning for discussion / conversation. The answer is no, because it may concern several people, which I understand very well in his answer Alex thought "space" but I also thought about the notifications.
In your example, it's 233, it could just as well be 2000, 5000 or 10.000, just now on my site dolphin I still had the case of a member whose registration date was 2011 and who suddenly wakes up, I have cases like that every day.
I know you're going to tell me, delete inactive accounts. No, I refuse to delete old accounts because I consider that an account is never dead IF his email address responds, so I only delete the notifications bounce and every day that passes me, in every case is my phylosophy.
I also do not show the dates of last connection and so people receive mail all the time, that's also why one day or another, so they come back on.
On dolphin it does not pose any problems it is cleaned and the guy does not end up with 50,000 notifications, yes, over 7 years is plausible, even see worse for a woman.
However, on Dolphin I also have this module: https://www.boonex.com/m/replies-reminder
It works a little like Una, and nothing was planned to empty notifications, the only solution was to follow each link one by one. I received many requests and then someone opened a topic on this topic, look at the attached screenshot. I translate to you: "Hey Mr. admin, how do I do when I have not come for some time and I find myself with 120 unread comments? There is no way to mark all read at once?"
You see, 120 notifications are already problematic ... So what do I say to my guy who has 5000? Sorry, the only solution is to delete your account and create a new one? No, I can not say that of course ...
For my problem on dolphin, I wrote to Anton, suggesting an automatic cleaning for notifications older than x days (configurable) He understood the problem since in return for my email I had the requested change .
You know what, by default it was 15 days, I automatically reduced to 10, it was still too much, I went to 7 days. Now it's good, but it's true that a reset button was more efficient, I did not think about it.

Excuse my intervention a bit long, I just wanted to explain that in the concrete it will not be possible"

57.0.4 (64 bits) on linux for me.

Indeed, I just tested the same text on my site, there, no problem.