There could be a Browser detection by `User-Agent` header. However how is this validation handled? My experience is that writing is just stopped when max length of content is reached. I did not see any validation message there so it can be send without user attention. Regular user just writes looking on keyboard and does not check written text (which is usually shorten by the end of field so there is not visible check of content completeness). Validation message is there needed from this reason IMO.