How to highlight (bold or italic) specific labels using geom_label() - r

Question

I am trying to highlight (either bold or italic) specific labels in a graph.
I am using geom_label but I don't know how to specify which groups should be highlighted.
Here is the data to build the table.
library(ggplot2)
library(dplyr)
library(ggalt)
library(cowplot)
library(tibble)
library(lubridate)
dates <- tribble( ~start_date, ~event, ~displ, ~model,
ymd(19680101), "No bold", 1, 'SP',
ymd(19820101), "Bold", 1, 'SP',
ymd(19800101), "No bold", 0.8, 'RCC',
ymd(20010101), "Bold", 0.8, 'RCC',
ymd(19740101), "No bold", -0.8,'OM',
ymd(19940101), "Bold", -0.8,'OM',
ymd(19560101), "No bold", -1,'SM',
ymd(20090101), "Bold", -1,'SM',
ymd(20010101), "No bold", 0.5,'US',
ymd(20090101), "Bold", 0.5,'US',
ymd(19890101), "Bold", -0.5,'LA')
Here is the function to plot the timeline.
shift_axis <- function(p, xmin, xmax, y=0){
g <- ggplotGrob(p)
dummy <- data.frame(y=y)
ax <- g[["grobs"]][g$layout$name == "axis-b"][[1]]
p + annotation_custom(grid::grobTree(ax, vp = grid::viewport(y=1, height=sum(ax$height))),
ymax=y, ymin=y) +
annotate("segment", y = 0, yend = 0, x = xmin, xend = xmax, size = 0.5,
arrow = arrow(length = unit(0.1, "inches"))) +
theme(axis.text.x = element_blank(),
axis.ticks.x=element_blank())
}
Finally, the graph where the labels go together in pairs (color coded).
vjust = ifelse(dates$displ > 0, -1.5, 1.5)
p1 <- dates %>%
ggplot(aes(start_date, displ)) +
geom_lollipop(point.size =1 ) +
#geom_text(aes(x = start_date, y = displ, label = event), data = data,
# hjust = 0, vjust = vjust, size = 4) +
geom_label(aes(x = start_date, y = displ, label = event, color=factor(model)),
data = data, hjust = 0, vjust = 0, size = 4) +
geom_point(aes(colour = factor(model)), size = 2) +
theme(axis.title = element_blank(),
axis.text.y = element_blank(),
axis.ticks.y = element_blank(),
axis.line = element_blank(),
axis.text.x = element_text(size = 12)) +
theme(axis.line = element_blank(),
panel.grid.major = element_blank(),
panel.grid.minor = element_blank(),
panel.border = element_blank(),
panel.background = element_blank()) +
expand_limits(x = c(ymd(19500101), ymd(20210101)), y = 1.2) +
scale_x_date(breaks = scales::pretty_breaks(n = 9)) +
theme(legend.position = "none")
timeline <- shift_axis(p1, ymd(19500101), ymd(20210101))
timeline
So, I am trying to highlight the labels in "Bold" (either bold or italic) and the "No bold" leave them as they appear in the plot.
Thanks in advance.