A maximum of 15 characters and "..." How? prntscr . com/h8qi7t

For that you would need to modify the file ..\controls\ForumActiveDiscussion.ascx.cs

and change line..

var topicSubject = this.Get<IBadWordReplace>().Replace(this.HtmlEncode(currentRow["Topic"]));

to

var topicSubject = this.Get<IBadWordReplace>().Replace(this.HtmlEncode(currentRow["Topic"])).Truncate(15);

A maximum of 15 characters and "..." How? prntscr . com/h8qi7t

For that you would need to modify the file ..\controls\ForumActiveDiscussion.ascx.cs

and change line..

var topicSubject = this.Get<IBadWordReplace>().Replace(this.HtmlEncode(currentRow["Topic"]));

to

var topicSubject = this.Get<IBadWordReplace>().Replace(this.HtmlEncode(currentRow["Topic"])).Truncate(15);

Excellent, it works). Thank you so much!