"!" exclamation when inserting GIF / Photo etc.
It's a bug, impacts any apps that use spans, e.g. Textra SMS, Chomp SMS, WhatsApp etc. Specific to Samsung device. Hopefully Samsung will fix it soon.
In the meantime we recommend and use the Google Keyboard, which does not have this issue. It's available in Google Play, search for "Gboard".
Another alternative is go to your Android Settings > General Management > Samsung Keyboard Settings > Suggest Text Corrections = Please deselect it.