Does recording a recommended fast on online forums for others to see fall under the ruling of showing off (riya')?

Naming a record of someone's fasting on a specific website as "group iftar" is baseless, because such a record is not considered iftar, neither linguistically nor Islamically. As for a person informing about their worship, if the intention is to speak of Allah's blessings and encourage righteousness and piety, there is no harm in it for one who is safe from ostentation and conceit. The scholars have mentioned the permissibility for a man to mention his worship to his trustworthy brethren, in affirmation of the Almighty's saying: "But as for the favor of your Lord, report [it]." However, whoever is not safe from ostentation and conceit, let him avoid that.